Selective deceleration brake control system

Abstract

A selective deceleration brake control system which enables the operator of an aircraft or other vehicle to preselect a rate of deceleration for the vehicle. The system produces a velocity reference signal which decreases in value at a rate indicative of the rate of vehicle deceleration selected by the operator. A signal indicative of actual wheel velocity is continuously produced and compared with the velocity reference signal to generate an error signal. The error signal is processed and used to produce a brake control signal. The system continuously controls braking effort to cause the vehicle to decelerate at the rate selected by the operator. The selective deceleration circuit cooperates with an anti-skid brake control circuit such that at any instant the circuit providing the higher brake release command will control.

Description

desired deceleration of the aircraft and appears at the output 86 of the deceleration generator 40.

When wheel spin-up occurs, the output of the comparator and hold circuit 42 is initially low. This forward biases controlled rectifier 88 and charges capacitor 90 through operational amplifier 92 until the output signal (the reference velocity) is close to the wheel velocity. When this happens, the output of the comparator and hold circuit 42 will then rise until controlled rectifier 88 is back biased, thereby preventing any further rise in this reference velocity or, in other words, in the voltage on capacitor 90. Capacitor 90 will now start to discharge at the rate determined by the voltage at input 94 of the deceleration generator 40. The voltage at the input 94 is determined by the pilot's setting of the deceleration rate selector 44. In other words, the deceleration rate selector 44 is a voltage source the output voltage of which may be selected by the pilot to set the desired deceleration rate.

To increase the accuracy of the rundown rate of the reference velocity voltage, a small precision capacitor 96 is used together with an operational amplifier 98 in a capacitance multiplier configuration. Assuming that the operational amplifiers are ideal, the capacitance multiplier functions as follows. If an operational amplifier is in linear region, then its inputs are at the same potential. Therefore, current through the resistor 102 is the same as the current through the resistor 104, and the current through resistor 106 is the same as the sum of the current through resistors 108 and 110. The voltage of operational amplifier 98 at output point 112 must be the same as at its inputs, and therefore the voltage drop across resistor 108 is the same as across resistor 110, and the current through resistor 110 may be computed from the following formula: ##EQU1## but I₁10 is the discharge current of capacitor 90 and therefore, multiplying I_total by ##EQU2## has the same effect as multiplying capacitor 90 by ##EQU3##

The PBM control circuit 54 functions to insure gradual brake reapplication after an initial brake release. Initially upon the application of an ON-ramp signal caused by the pilot closing his ON-ramp selector switch 48, a 300 millisecond-wide pulse from the ON-ramp control circuit 62 is applied to the input 126 of the PBM control circuit 54 via the lead 128. This pulse will cause a capacitor 132 to charge rapidly to the maximum PBM voltage. This maximum PBM voltage is then applied via the leads 134, 136, and 138 to the OR amplifier 56. This causes the OR amplifier to have a maximum output and will result in a maximum brake release. After this initial pulse is removed from the capacitor, the capacitor 132 will start to discharge through a resistor 140. As the capacitor discharges, the PBM voltage decreases and a gradual brake application is obtained. This is what is referred to as the ON-ramp brake application. Following this gradual ON-ramp brake application, the only input to the PBM circuit 54 during normal braking operation is from the comparator and hold circuit 42 via the lead 43 through a resistor 142. This output from the comparator and hold circuit 42 is the error velocity signal. The error velocity signal from the comparator and hold circuit 42 is integrated by the PBM control circuit 54 and more particularly by the capacitor 132 and an operational amplifier 144. Resistors 146, 148, and 150 set the actuation threshold for the integration process. A controlled rectifier 152 is a clamping diode that limits the PBM voltage when there is no input.

The OR amplifier 56 is the output circuit for the entire selective deceleration control circuit 10. The output of the OR amplifier 56 occurs at the output points 162 and 164. The signals at these output points 162 and 164 are transmitted via the leads 58 and 60 to the valve drivers 36 and 36a, respectively. As mentioned previously, the output signal from the PBM control circuit 54, which in essence is an integral function of the error velocity signal from the comparator and hold circuit 42, is applied to the OR amplifier 56 via the lead 138 through the resistors 166 and 168, and finally to operational amplifiers 170 and 172. In addition, the error velocity signal from the comparator and hold circuit 42 is applied directly to the OR amplifier 56 at input point 174 through the capacitor 176 from the output of the operational amplifier 78 of the comparator and hold circuit 42 via the lead 178. Thus, the deceleration brake control output signal of the OR amplifier circuit 56 is a composite signal comprising the deceleration control signal which is an integral function of the error velocity signal as the main control component and a direct or proportional function of the error velocity signal as a transient correcting component. As mentioned previously, the output of the OR amplifier 56 is transmitted to the valve drivers 36 and 36a through an OR gate 62 and an OR gate 62a (FIG. 1), and this signal is OR-ed with the output signal from the anti-skid control circuits 12 and 12a. If the OR amplifier output is higher than the output of the anti-skid control circuits 12 or 12a, then the OR amplifier output will control the valve driver 36 or 36a, but if the output from the anti-skid control circuit is higher, then the anti-skid control circuit signal will control the valve driver 36. This occurs because the controlled rectifiers 178 and 180 are back biased.

To assure proper operation, a zener diode 182 is provided which regulates the B plus voltage on the operational amplifiers 170 and 172 and maintains them at 18 volts in the preferred embodiment. A capacitor 185 prevents power loss transients from affecting the outputs of the OR amplifier 56. A pair of resistors 184 and 186 set the OR amplifier threshold, i.e. the PBM voltage required to cause an OR amplifier output that exceeds the valve driver threshold. The OR amplifier 56 receives its B plus voltage from the ON-ramp voltage circuit 40, and thus the ON-ramp voltage circuit 40 serves to gate the output of the OR amplifier 56. This is done so that no failure on the selective deceleration circuit 10 can cause a brake release if the ON-ramp voltage is removed.

In normal operation, when the ON-ramp voltage is applied either by the pilot closing the switch 48 or by suitable logic circuitry, the transistor 206 is on and the transistor 208 is off, thereby permitting normal operation of the OR amplifier 56. If the ON-ramp voltage is removed, then the transistor 206 will begin to turn off and when the breakdown voltage of the zener diode 210 is exceeded, the transistor 208 will then turn off. This removes the OR amplifier output from the valve driver input by grounding the point 212 of the OFF-ramp ramp circuit 50 and thereby also the outputs of the operational amplifier 170 and 172 of the OR amplifier 56. A capacitor 184 external to the OR amplifier circuit 56 introduces a delay of approximately 100 milliseconds between the time of the removal of the ON-ramp voltage and the removal of the OR amplifier output.

Immediately upon the application of an ON-ramp voltage from the ON-ramp control circuit 40, the ON-ramp hold circuit 62 generates an output pulse at the output point 228. This pulse is applied to the input of the PBM control circuit 54 via the leads 230, 130, and 128 and causes the PBM control circuit 54 to generate maximum PBM voltage thereby creating an initial brake release prior to ON-ramp brake application and prior to the generation of the error velocity signal by the comparator and hold circuit 42.

The reference velocity voltage from the deceleration generator 40 is applied to the ON-ramp hold circuit 62 at point 232 via the leads 234 and 41. Since during spin-up this voltage will change in a positive direction, the normally off transistor 236 will turn on and discharge the capacitor 238. After spin-up, the voltage at the point 232 will no longer change in a positive direction and therefore will turn off the transistor 236. The capacitor 238 will now start to charge and when its voltage exceeds the breakdown voltage of the zener diode 240 and the forward voltage of the controlled rectifier 242 and the base emitter voltage of the transistor 244, the transistor 244 will turn on. Transistors 244 and 246 are in a latching configuration so once they have turned on, they will remain on so long as the ON-ramp voltage is applied. When the transistors 244 and 246 turn on, the pulse in the PBM control circuit 54 is terminated. The time delay between the ON-ramp application and the turn on of transistors 244 and 246 is approximately 300 milliseconds. A zener diode 248 provides additional voltage regulation (transient protection). The capacitor 238 prevents the transistors 244 and 246 from unlatching during any power loss transients.

The OFF-ramp control circuit 50 functions to cause a gradual brake release after an OFF-ramp input voltage is applied due to the pilot closing the OFF-ramp selector switch 52. The OFF-ramp control circuit 50 is in a closed loop differentiator configuration. In normal braking operation when there is an ON-ramp input but no OFF-ramp input, the transistor 282 is held on. This will force the output of the operational amplifier 284 to approximately plus 4 volts and since there is no OFF-ramp input, the controlled rectifier 282 will be back biased thereby preventing the loading of the input of the PBM control circuit 54.

When the OFF-ramp is applied, the transistor 282 is turned off, and this permits normal operation of the OFF-ramp control circuit 50. The OFF-ramp voltage is now applied to the output point 288 and through the output of the point 290 to the input of the PBM control circuit 54 via the leads 292, 130, and 128. The PBM voltage will now increase at a rate proportional to the input current, and this will therefore also be the case of the output of the OR amplifier 56 thus causing a release of brake pressure. This output from the OR amplifier 56 is transmitted via lead 294 to the OFF-ramp control circuit 50 where it is differentiated by the capacitor 296 and the resistor 290 and is amplified by the operational amplifier 284. The output of the operational amplifier 284 will therefore have a voltage amplitude that is proportional to the slope of the output of the OR amplifier circuit 56. Since the output of the operational amplifier 144 of the PBM control circuit 54 will go in a negative direction from the reference, part of the input current through the resistor 150 of the PBM control circuit 54 will now be shunted from the PBM control circuit input into the operational amplifier 144. Equilibrium will therefore be established, and the rate of brake release will be constant. Controlled rectifiers 302 and 304 form a part of the gate for the OR amplifier 56. When the ON-ramp is removed, the point 212 is grounded, and this removes the OR amplifier output from the valve driver circuit 36 as described above.

As mentioned previously, the function of the pressure balance amplifiers 66 and 66b is to equalize the brake load distribution of the outboard and inboard wheel groups which are controlled by the selective deceleration circuits 10 and 10b, respectively (see FIG. 1). If this were not done, then one wheel group could carry all or most of the brake load while the other wheel group carried only a small brake load. The brake load information (the PBM voltage) from the outboard wheel group is applied to the input point 330 of the balance amplifier 66 via the leads 134 and 136. This PBM voltage is also applied to the input of the balance amplifier 66b via the leads 134 and 136b. The brake load information from the inboard wheel group is applied to the input point 332 of the balance amplifier 66 via the leads 334 and 336 and is also applied to the input of the balance amplifier 66b via the lead 336b (FIG. 1). The output from the pressure balance amplifier 66 is applied to the input of the PBM control circuit 54b via the lead 359. Similarly, the output of pressure balance amplifier 66b is applied to the input of PBM control circuit 54 via the leads 357 and 128. If the two inputs to the pressure balance amplifier 6 are approximately the same, the output of the operational amplifier 338 is less than 4 volts and will not affect the PBM control circuit 54b associated with the inboard wheels. But if the voltage at the points 330 is less than that at point 332, then the output of the operational amplifier 338 goes higher than 4 volts and will cause an increase of the PBM voltage in PBM control circuit 54b (FIG. 1) until the input at the points 330 and 332 is again in balance. It should be noted here that the PBM reference is plus 4 volts, and therefore, plus 4 volts with respect to ground out of the PBM control circuit 54 means zero PBM voltage and zero volts with respect to ground means maximum PBM voltage. A similar balancing control takes place in the pressure balance amplifier 66b (FIG. 1) which if an inbalance occurs, controls the PBM voltage in PBM control circuit 54.

As mentioned heretofore, the transistor 82 of the comparator and hold circuit 42 is off at all times except for a short time (approximately 300 milliseconds) at the beginning of the ON-ramp. Its function is to assure that there is no PBM voltage buildup due to pressure balance amplifier unbalance until the entire system has stabilized and thus the pressure balance amplifiers 66 and 66b only affect the selective deceleration control circuits 10 and 10b after stabilization.

The voltage regulator circuit 70 does not appear in FIGS. 1 and 3 and is disclosed to show one method for obtaining the various voltages needed to operate the selective deceleration control circuit 10. However, it will be recognized that several other methods may be utilized to obtain the required operating voltages. The voltage regulator circuit 70 takes the 24 volt DC input voltage and converts it to a 15 volt DC source. The voltage regulator is of the series type (emitter follower) where the voltage at the base of a path transistor 364 is determined by the voltage across the controlled rectifier 366 and the zener diode 368. Zener diode 368 is rated at 14.6 volts, and the forward voltage of the controlled rectifier 370 is 0.7 volts. Therefore, the base voltage of the transistor 364 will be approximately 15.3 volts where the voltage at the emitter (output voltage) will be approximately 14.6 volts. Transistors 372 and 374 form a voltage follower that supplies the plus 4 volt DC to the rest of the selective deceleration control circuit 10. The 4 volts from the main power source of the aircraft enter the voltage regulator circuit 70 at the points 376 and 378 and are applied to the base of the transistor 372 through the resistors 380 and 382. Since the base emitter voltage drops, the transistors 372 and 374 cancel each other, the voltage at the emitter of the transistor 374 (output voltage) will be approximately the same as the input voltage or plus 4 volts. The capacitors 384 and 386 provide additional filtering. The resistor 388 reduces the power dissipation in the transistor 364 and also provides isolation from the 24 volt input.

It will be recognized that the schematic diagrams shown in FIGS. 4a, 4b, 4c, and 4d represent one illustrative embodiment of the invention. The various circuit elements are tabulated below as to value or type number. It will be recognized, however, that these values are exemplary and are merely illustrative of the invention, and various modifications may be made without departing from the spirit and scope of the invention. All capacitor values are in microfarads except as otherwise noted. All resistor values are in ohms or kilo except as otherwise noted.

______________________________________
DECELERATION GENERATOR-40
VALUE OR
ELEMENT NUMBER          TYPE NUMBER
______________________________________
90                     1 μf
96                     .0022 μf
102                     57.6K
104                     57.6K
106                     4.99K
108                     4.99K
110                     511K
114                     8.87K
116                     1.62K
118                     178K
120                     0.1 μf
122                     511K
124                     10K
125                     909 Ω
127                     3.74K
88                     CD5645
92                     S101
98                     LM207
______________________________________
COMPARATOR AND HOLD CIRCUIT-42
VALUE OR
ELEMENT NUMBER          TYPE NUMBER
______________________________________
71                     4.7 μf
73                     2.37K
75                     13.3K
77                     150K
79                     150K
83                     301K
85                     2K
87                     IN751A
78                     S101
80                     S101
82                     2N956
______________________________________
PBM CONTROL CIRCUIT-54  VALUE OR
ELEMENT NUMBER          TYPE NUMBER
______________________________________
132                     2.2 μf
140                     499K
142                     40.2K
146                     24.3K
148                     130K
150                     1K
160                     100 pF
144                     42-15570
______________________________________
OR AMPLIFIER-56         VALUE OR
ELEMENT NUMBER          TYPE NUMBER
______________________________________
166                     150K
168                     150K
176                     .047 μf
184                     150K
185                     150 μf
186                     280K
188                     1K
190                     1K
192                     10K
198                     150K
200                     46.4K
202                     280K
204                     1K
196                     IN649
182                     UZ818
170                     S101
172                     S101
______________________________________
ON-RAMP CONTROL CIRCUIT-46
VALUE OR
ELEMENT NUMBER          TYPE NUMBER
______________________________________
214                     20K
216                     5.11K
218                     4.53K
220                     10K
222                     2.2 μf
224                     7.5K
226                     IN649
210                     IN5234
208                     2N956
206                     2N956
______________________________________
ON-RAMP HOLD CIRCUIT-62 VALUE OR
ELEMENT NUMBER          TYPE NUMBER
______________________________________
258                     3.32K
262                     1K
264                     10K
268                     15K
270                     6.8 μf
271                     10K
272                     6.8
274                     2K
276                     2K
252                     CD5645
266                     IN649
240                     IN5230
248                     UZ5720
236                     2N956
246                     2N2605
244                     2N930
______________________________________
OFF-RAMP CONTROL CIRCUIT-50
VALUE OR
ELEMENT NUMBER          TYPE NUMBER
______________________________________
296                     22 μf
298                     49.9
206                     2K
310                     750
312                     .68 μf
316                     383K
317                     249K
318                     68.1K
322                     1.21K
324                     200K
284                     S101
282                     2N930
286                     CD5645
323                     CD5645
______________________________________
PRESSURE BALANCE AMPLIFIER-62
VALUE OR
ELEMENT NUMBER          TYPR NUMBER
______________________________________
340                     51.1K
342                     51.1K
344                     2.2 μf
346                     10K
348                     10K
350                     200K
352                     2.2 μf
354                     200K
358                     49.9K
360                     2K
362                     1M
338
______________________________________
VOLTAGE REGULATOR-70    VALUE OR
ELEMENT NUMBER          TYPE NUMBER
______________________________________
380                     2K
382                     2K
384                     6.8 μf
386                     0.1 μf
388                     150 Ω
392                     750 Ω
394                     1.5K
396                     4.32K
364                     2N1893
372                     2N930
374                     2N2605
368                     1N4058
______________________________________

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

Claims

1. A brake control system for applying and controlling the brake application means for a wheel of a vehicle independently of operator brake application, comprising:

signal generating means for producing a wheel speed signal that is a function of the rotational speed of said wheel;

anti-skid control means for receiving and processing said wheel speed signal to provide an anti-skid brake control signal;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of vehicle deceleration;

comparison means for comparing said wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said wheel speed signal and said reference velocity signal;

control means for providing a signal to said brake application means to apply brake pressure to said wheel independently of operator brake application and response to said error signal to provide a selected deceleration control signal for controlling said brake pressure in order to maintain said desired rate of deceleration; and

means for preventing said brake application means from applying said brake pressure in response to said deceleration brake control signal and for applying brake pressure in response to said anti-skid brake control signal when said anti-skid brake control signal commands a lower brake pressure than does said deceleration brake control signal.

2. The invention defined in claim 1 wherein said reference generating means includes means for establishing an initial reference velocity signal value based on the maximum value attained by said wheel speed signal during wheel spin-up.

3. The invention defined in claim 1 wherein said brake control system further comprises a deceleration control turn-on means for energizing said deceleration control signal generating means and causing said deceleration control means to provide an initial deceleration control signal of maximum, value commanding a full brake release followed by a gradual decrease from said maximum value to permit a corresponding gradual increase in brake pressure.

4. The invention defined in claim 1 wherein said brake control system further comprises means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means to provide incident to said de-actuation a deceleration control signal of gradually decreasing value to permit a gradual decrease in brake pressure.

5. The invention of claim 1 wherein said control means provides said signal initially upon the actuation of a switch means by the operator.

6. A brake control system for applying and controlling the brake application means associated with each wheel of a pair of brake loaded-bearing wheels of an aircraft independently of operator brake application, comprising:

signal generating means for each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

anti-skid control means for each of said wheels for receiving and processing said wheel speed signal to provide an anti-skid brake control for control signal for control of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of vehicle deceleration;

averaging means responsive to the wheel speed signal associated with each of said wheels to form an average wheel speed signal therefrom;

comparison means for comparing said average wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal and said reference velocity signal;

control means for providing a signal to said brake application means to apply brake pressure to each of said wheels independently of operator brake application and responsive to said error signal to provide a selected deceleration control signal for controlling said brake pressure in order to maintain said desired rate of deceleration; and

means for preventing said brake application means from applying said brake pressure in response to said brake control signal and for applying brake pressure in response to said anti-skid brake control signal when said anti-skid brake control signal commands a lower brake pressure than does said deceleration brake control signal.

7. The invention defined in claim 6 wherein said reference generating means includes means for establishing an initial reference velocity signal value based on the maximum value attained by said wheel speed signal during wheel spin-up.

8. The invention defined in claim 6 wherein said brake control system further comprises a deceleration control turn-on means for energizing said deceleration control signal generating means and causing said deceleration control means to provide an initial deceleration control signal of maximum value commanding a full brake release followed by a gradual decrease from said maximum value to permit a corresponding gradual increase in brake pressure.

9. The invention defined in claim 6 wherein said brake control system further comprises means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means to provide incident to said de-actuation a deceleration control signal of gradually decreasing value to permit a gradual decrease in brake pressure.

10. The invention defined in claim 6 wherein said deceleration brake control signal comprises a time integral function of said error signal.

11. The invention defined in claim 10 wherein said deceleration control means includes circuit means having a predetermined actuation threshold level and wherein said time integral function is a time integral function of both positive and negative variation of said error signal from said threshold level.

12. The invention defined in claim 11 wherein said deceleration brake control signal further comprises a nonintegral, proportional function of said error signal.

13. A brake control system, for an aircraft having plural groups of braked load-bearing wheels for applying and controlling a brake application means for said wheels independently of operator brake application, said system separate inboard and outboard wheel groups in which the wheels in each group are symmetrically mounted on opposite sides of the aircraft, comprising:

brake application means for providing brake pressure to each wheel;

anti-skid control means for providing an anti-skid brake control signal;

signal generating means associated with each of said wheels for producing a first signal that is related proportional to the rotational speed of its associated wheel;

reference generating means for generating a velocity reference signal having a selectively variable rate of decrease;

rate selector means for manually selecting said modifying said reference generating means for producing a reference signal indicative of a the desired rate of vehicle deceleration;

separate averaging means in for each of said wheel groups responsive to the first signal associated with each of said wheels in said group to form an average for continuously determining the average speed of said wheels in each said group and for forming an analog signal therefrom which is a function of said average speed of said wheels;

comparison means for each of said wheel groups for comparing said average analog signals for the associated wheel group with said reference signal for generating an error signal indicative of the difference between said average analog signal for the associated wheel group and said reference signal;

modulating means for each of said wheel groups responsive to said error signal for producing a modulating brake signal when said error signal exceeds a predetermined threshold level, said modulating brake signal including a time integral function of both positive and negative variations of said error signal from said threshold level;

control means associated with each group of wheels and responsive to said modulating brake signal for providing a deceleration brake control signal to said brake application means to apply brake pressure to said wheels independently of operator brake application and responsive to said error signal to provide a deceleration control signal for controlling said brake pressure in order to maintain said desired rate of deceleration, said control means including pressure balancing means associated with each of said modulating means for comparing the modulating brake signal of said associated modulating means with the modulating brake signal of another modulating means and causing the other modulating means to produce a modulating brake signal whose valve is not less than that of the associated modulating brake signal, thereby equalizing brake load distribution between said wheel groups; and

means for preventing said brake application means from applying said brake pressure in response to said deceleration brake control signal for said group of wheels and for applying brake pressure in response to said anti-skid brake control signal when said anti-skid brake control signal commands a lower brake pressure than does said deceleration brake control signal;

means for submitting an on-ramp signal to said modulating means to cause said modulating means to provide an initial deceleration brake control signal to gradually increase brake pressure; and

means for submitting an off-ramp signal to said modulating means to cause said modulating means to provide a final deceleration brake control signal to gradually remove brake pressure.

14. The invention defined in claim 13 further comprising: a means associated with each of said control means for comparing the output thereof with the output of another of said control means associated with another wheel group to cause the output of the associated control means to command a brake pressure level

not less than that commanded by said other control means. 15. The invention brake control system of claim 13 where in wherein each of said control means provides said deceleration brake control signal initially upon the

actuation of a switch means by the operator. 16. A deceleration control system for applying and controlling the brake application means associated with each wheel of group of braked load-bearing wheels of an aircraft, independently of operator brake application, comprising:

inboard and outboard wheels, each wheel having a brake;

separate brake application means for providing brake pressure to said wheels;

separate inboard and outboard wheel groups in which the wheels in each of said groups are mounted on opposite sides of the aircraft;

signal generating means for each of said wheels for producing a first signal that is related proportional to the rotational speed of its associated wheel;

reference generating means for generating a velocity reference signal having a selectively variable rate of decrease;

rate selector means for manually selecting said modifying said reference generating means for producing a reference signal indicative of a the desired rate of vehicle deceleration;

separate averaging means for each of said wheel groups responsive to the first signal associated with each of said wheels to form an for continuously determining the average speed of said wheels and for forming an analog signal therefrom which is a function of said average speed of said wheels;

comparison means for comparing said average analog signal with said reference signal for generating an error signal indicative of the difference between said average analog signal and said reference signal; and

modulating means responsive to said error signal for producing a modulating brake signal when said error signal exceeds a predetermined threshold level, said modulating brake signal including a time integral function of both positive and negative variations of said error signal from said threshold level;

control means responsive to said modulating brake signal for providing a deceleration brake control signal to said brake application means to apply brake pressure to said wheels independently of operator brake application and responsive to said error signal to provide a selected deceleration control signal for controlling said brake pressure in order to maintain said desired rate of deceleration, said control means including separate pressure balancing means associated with each of said modulating means for comparing the modulating brake signal produced thereby with the modulating brake signal produced by another of said modulating means and producing an output that is applied to said other modulating means to command a deceleration brake control signal whose value is not less than the deceleration brake control signal commanded by said associated modulating means, thereby causing the braking load to be evenly distributed between wheel groups;

means for submitting an on-ramp signal to said modulating means to cause said modulating means to provide an initial deceleration brake control signal to gradually increase brake pressure; and

means for submitting an off-ramp signal to said modulating means to cause said modulating means to provide a final deceleration brake control signal

to gradually remove brake pressure. 17. The invention deceleration control system defined in claim 16 wherein each of said reference generating means includes means for establishing an initial reference signal value based on the maximum value

attained by said average signal during wheel spin-up. 18. The invention deceleration control system defined in claim 11 16 wherein said brake control system further comprises a control turn-on means for energizing said control means and causing said control means for submitting an on-ramp signal includes means to provide for providing an initial deceleration brake control signal of maximum value commanding a full brake release followed by a gradual decrease from said maximum value to permit a corresponding gradual increase in brake pressure.

19. The invention defined in claim 16 wherein said brake control system further comprises means for deactuating said control means and for causing said control means to provide incident to said deactuation a deceleration control signal of gradually decreasing

value to permit a gradual decrease in brake pressure. 20. The invention deceleration control system defined in claim 16 wherein said deceleration brake control signal comprises a time

integral function of said error signal. 21. The invention deceleration control system defined in claim 20 wherein said control means includes circuit means having a predetermined actuation threshold level and wherein said time integral function is a time integral function of both positive and negative variation of said

error signal from said threshold level. 22. The invention deceleration control system defined in claim 21 wherein said deceleration brake control signal further comprises a nonintegral non-integral, proportional function of

said error signal. 23. The invention deceleration control system of claim 16 wherein said control means provides said signal initially upon the actuation of a switch means by the operator.

A deceleration control system for an aircraft having plural groups of brake load-bearing wheels, separate inboard and outboard wheel groups in which the wheels in each said group are symmetrically mounted on opposite side of the aircraft, for applying and controlling a brake application means for said wheels independently of operator brake application, said system comprising:

brake application means for applying brake pressure to said wheels;

signal generating means associated with each of said wheels for producing a first signal that is related proportional to the rotational speed of its associated wheel;

reference generating means for generating a velocity reference signal having a selectively variable rate of decrease;

rate selector means for manually selecting said modifying said reference generating means for producing a reference signal indicative of a the desired rate of vehicle deceleration;

separate averaging means for each of said wheel groups responsive to the first signal associated with each of said wheels in said group to form an for continuously determining the average speed of said wheels and for forming an analog signal therefrom which is a function of said average speed of said wheels;

comparison means for each of said wheel groups for comparing said average analog signal for the associated wheel group with said reference signal for generating an error signal indicative of the difference between said average analog signal for the associated wheel group and said reference signal; and

modulating means for each of said wheel groups, each responsive to said error signal for producing a modulating brake signal when said error signal exceeds a predetermined threshold level, each of said modulating brake signals including a time integral function of both positive and negative variations of said error signal from said threshold level;

control means associated with each wheel group of wheels and responsive to said modulating brake signal for providing a deceleration brake control signal to said brake application means to apply brake pressure to said wheels independently of operator brake application and responsive to said error signal to provide a deceleration control signal for controlling said brake pressure in order to maintain said desired rate of deceleration, said control means including pressure balancing means associated with each of said modulating means for comparing the modulating brake signal of said associated modulating means with the modulating brake signal of another modulating means and causing the other modulating means to produce a modulating brake signal whose value is not less than that of the associated modulating brake signal, thereby equalizing brake load distribution between wheel groups;

means for submitting an on-ramp signal to said modulating means to cause said modulating means to provide an initial deceleration brake control signal to gradually increase brake pressure; and

means for submitting an off-ramp signal to said modulating means to cause said modulating means to provide a final deceleration brake control signal

to gradually remove brake pressure. 25. The invention deceleration control system defined in claim 24 wherein each of said reference generating means includes means for establishing an initial reference signal value based on the maximum value

attained by said average signal during wheel spin-up. 26. The invention deceleration control system defined in claim 24 wherein said brake control system further comprises for each of said wheel groups a control turn-on means for energizing said control means associated therewith and causing said associated control means for submitting said on-ramp signal includes means to provide for providing an initial brake deceleration control signal of maximum value commanding a full brake release followed by a gradual decrease from said maximum value to permit a corresponding gradual increase in brake pressure.

27. The invention defined in claim 24 wherein said brake control system further comprises for each of said wheel groups means for deactuating said control means associated therewith and for causing said associated control means incident to said deactuation to provide a deceleration control signal of gradually decreasing value to permit a gradual decrease in brake

pressure. 28. The invention deceleration control system defined in claim 24 wherein each said deceleration brake control signal comprises a time integral function of said error signal.

The invention deceleration control system defined in claim 28 wherein each said control means includes circuit means having a predetermined actuation threshold level and wherein said time integral function is a time integral function of both positive and

negative variation of said error signal from said threshold level. 30. The invention deceleration control system defined in claim 29 wherein each said deceleration brake control signal further comprises a non-integral, proportional function of said error signal.

31. The invention defined in claim 30 further comprising:

a means associated with each of said control means for comparing the time integral function formed thereby with the time integral function formed by another of said control means associated with another wheel group to cause the time integral function formed by said associated control means to command a brake pressure level not less than that commanded by said other

control means. 32. A brake control system for controlling the brake application means for a wheel of a vehicle comprising:

analog signal generating means for producing a wheel speed signal that is a function of the rotational speed of said wheel;

anti-skid control means for receiving and processing said wheel speed signal to provide an anti-skid brake control signal;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of wheel deceleration;

comparison means for comparing said wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said wheel speed signal and said reference velocity signal;

deceleration control signal generating means responsive to said error signal to provide deceleration brake control signal;

gate means for receiving and comparing said anti-skid brake control signal and said deceleration brake control signal to transmit for control of said brake application means the control signal which commands the lower brake pressure; and

means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means to provide incident to said deactuation a deceleration control signal of gradually

decreasing value to permit a gradual decrease in brake pressure. 33. A brake control system for controlling the brake application means associated with each wheel of a pair of braked load-bearing wheels of an aircraft comprising:

analog signal generating means for each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

anti-skid control means for each of said wheels for receiving and processing said wheel speed signal to provide an anti-skid brake control signal for control of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of wheel deceleration;

averaging means responsive to the wheel speed signal associated with each of said wheels to form an average wheel speed signal therefrom;

comparison means for comparing said average wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal and said reference velocity signal;

deceleration control signal generating means responsive to said error signal to provide a deceleration brake control signal;

gate means for each of said wheels for receiving and comparing said anti-skid brake control signal for its associated wheel and said deceleration brake control signal to transmit for control of the brake application means for its associated wheel the control signal which commands the lower brake pressure; and

means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means to provide incident to said deactuation a deceleration control signal of gradually

decreasing value to permit a gradual decrease in brake pressure. 34. A brake control system for an aircraft having plural groups of braked load-bearing wheels, said system comprising:

analog signal generating means associated with each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

anti-skid control means for each of said wheels receiving and processing said wheel speed signal to provide an anti-skid brake control signal for control of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of deceleration;

averaging means for each of said wheel groups for each of the wheels in its associated wheel group to form an average wheel speed signal therefrom;

comparison means for each of said wheel groups for comparing said wheel speed signal for the associated wheel group with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal for the associated wheel group and said reference velocity signal;

deceleration control signal generating means for each of said wheel groups responsive to said error signal for the associated wheel group to provide a deceleration brake control signal for the associated wheel group;

gate means for each of said wheels for receiving and comparing said anti-skid brake control signal for said wheel and said deceleration brake control signal for the associated wheel group to transmit for control of brake application means associated with said wheel the control signal which commands the lower brake pressure; and

a pressure balance means associated with each of said deceleration control signal generating means for comparing an output thereof with an output of another deceleration control signal generating means for another wheel group to cause the output of the associated deceleration control signal generating means to command a brake pressure level not less than that

commanded by said other deceleration control signal generating means. 35. A decelerational control system controlling the brake application means for a wheel of a vehicle comprising:

analog signal generating means for producing a wheel speed signal that is a function of the rotational speed of said wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of deceleration; p1 comparison means for comparing said wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said wheel speed signal and said reference velocity signal;

control means responsive to said error signal to provide a selected deceleration brake control signal; and

means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means incident to said deactuation to provide a deceleration control signal of gradually

decreasing value to permit a gradual decrease in brake pressure. 36. A deceleration control system controlling the brake application means associated with each wheel of group of braked load-bearing wheels of an aircraft comprising:

analog signal generating means for each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of deceleration;

averaging means responsive to the wheel speed signal associated with each of said wheels to form an average wheel speed signal therefrom;

comparison means for comparing said average wheel speed signal with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal and said reference velocity signal;

deceleration control signal generating means responsive to said error signal to provide a deceleration brake control signal; and

means for deactuating said deceleration control signal generating means and for causing said deceleration control signal generating means to provide incident to said deactuation a deceleration control signal of gradually

decreasing value to permit a gradual decrease in brake pressure. 37. A deceleration control system for an aircraft having plural groups of braked load-bearing wheels, said system comprising:

analog signal generating means associated with each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of deceleration;

averaging means for each of said wheel groups for each of the wheels in its associated wheel group to form an average wheel speed signal therefrom;

comparison means for each of said wheel groups for comparing said wheel speed signal for the associated wheel group with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal for the associated wheel group and said reference velocity signal;

deceleration control signal generating means for each of said wheel groups responsive to said error signal for the associated wheel group to provide a deceleration brake control signal for the associated wheel group; and

means for each of said wheel groups for deactuating said deceleration control signal generating means associated therewith and for causing said associated deceleration control signal generating means incident to said deactuation to provide a deceleration control signal of gradually

decreasing value to permit a gradual decrease in brake pressure. 38. A deceleration control system for an aircraft having plural groups of braked load-bearing wheels, said system comprising:

analog signal generating means associated with each of said wheels for producing a wheel speed signal that is a function of the rotational speed of its associated wheel;

reference generating means for generating a reference velocity signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of deceleration;

averaging means for each of said wheel groups for each of the wheels in its associated wheel group to form an average wheel speed signal therefrom;

comparison means for each of said wheel groups for comparing said wheel speed signal for the associated wheel group with said reference velocity signal for generating an error signal indicative of the difference between said average wheel speed signal for the associated wheel group and said reference velocity signal;

deceleration control signal generating means for each of said wheel groups responsive to said error signal for the associated wheel group to provide a deceleration brake control signal for the associated wheel group; and

a pressure balance means associated with each of said deceleration control signal generating means for comparing the signal formed thereby with the signal formed by another deceleration control signal generating means for another wheel group to cause the signal formed by said associated deceleration control signal generating means of the associated deceleration control signal generating means to command a brake pressure level not less than that commanded by said other deceleration control

signal generating means. 39. A brake control system for applying and controlling a brake application means for a wheel of a vehicle independently of operator brake application comprising:

signal generating means for producing a first signal that is proportional to the speed of said wheel;

reference generating means for generating a velocity reference signal having a selectively variable rate of decrease;

rate selector means for manually selecting a rate of decrease of said reference velocity signal indicative of a desired rate of vehicle deceleration;

comparison means for comparing said first signal with said reference signal for generating an error signal indicative of the difference between said first signal and said reference signal; and

control means for providing a signal to said brake application means to apply brake pressure to said wheel independently of operator brake application and responsive to said error signal to provide a selected deceleration brake control signal for controlling said brake pressure in

order to maintain said desired rate of deceleration. 40. The invention defined in claim 39 wherein said deceleration brake control signal

comprises a time integral function of said error signal. 41. The invention defined in claim 40 wherein said deceleration control means includes circuit means having a predetermined actuation threshold level and wherein said time integral function is a time integral function of both positive and negative variation of said error signal from said threshold level.

The invention defined in claim 40 wherein said deceleration brake control signal further comprises a non-integral, proportional function of

said error signal. 43. The invention defined in claim 39 wherein said deceleration control system further comprises a deceleration control turn-on means for energizing said control means and causing said control means to provide an initial deceleration control signal of maximum value commanding a full brake release followed by a gradual decrease from said maximum value to permit a corresponding gradual increase in brake

pressure. 44. The invention defined in claim 39 wherein said deceleration control system further comprises means for deactuating said control means and for causing said control means incident to said deactuation to provide a deceleration control signal of gradually decreasing value to permit a

gradual decrease in brake pressure. 45. The invention defined in claim 39 wherein said deceleration brake control signal comprises a time integral

function of said error signal. 46. The invention defined in claim 45 wherein said control means includes circuit means having a predetermined actuation threshold level and wherein said time integral function is a time integral function of both positive and negative variation of said

error signal from said threshold level. 47. The invention defined in claim 45 wherein said deceleration brake control signal further comprises a

nonintegral, proportional function of said error signal. 48. The invention of claim 39 wherein said control means provides said signal initially upon the actuation of a switch means by the operator.