Vehicular brake-by-wire system

• US 6,293,632 B1
• Filed: 06/11/1999
• Issued: 09/25/2001
• Est. Priority Date: 06/11/1999
• Status: Expired due to Fees

• Current Assignee: Power Systems Technologies Limited
• Original Assignee: Power Systems Technologies Limited
• Inventors: Grote, John F., Tarbet, J. Denton
• Primary Examiner(s): Oberleitner, Robert J.
• Assistant Examiner(s): SY, MARIANO ONG
• Application Number:
  US09/332,299
• Time in Patent Office: 837 Days
• Field of Search: 303/177, 303/3, 303/112, 303/122.08, 188/156, 188/158, 188/370, 188/72.1, 188/1.11 R, 188/1.11 E, 192/30.W
• US Class Current: 303/112
• CPC Class Codes: B60T 13/741 acting on an ultimate actuator
• CPC Class Codes: B60T 2270/82 Brake-by-Wire, EHB
• CPC Class Codes: B60T 7/042 by electrical means, e.g. using travel or force sensors
• CPC Class Codes: B60T 8/326 Hydraulic systems
• CPC Class Codes: B60T 8/52 Torque sensing, i.e. wherein the braking action is controlled by forces producing or tending to produce a twisting or rotating motion on a braked rotating member
• CPC Class Codes: F16D 2066/005 Force, torque, stress or strain
• CPC Class Codes: F16D 2121/28 using electrostrictive or magnetostrictive elements, e.g. piezoelectric elements
• CPC Class Codes: F16D 2125/10 Plural pistons interacting by fluid pressure, e.g. hydraulic force amplifiers using different sized pistons
• CPC Class Codes: F16D 55/227 by two or more pins
• CPC Class Codes: F16D 65/18 adapted for drawing members together , e.g. for disc brakes

Abstract

The present invention provides an improved torque actuator control system using data inputs from an operator controlled input transducer relating to the desired torque output of a controlled member and inputs concerning the directly measured speed and torque of the controlled member. The improved torque actuator control circuit uses the inputs to generate an output command to the controlled member that results in the direct application of the desired torque output from the controlled member.

Claims

1. A brake system for a vehicle, comprising:

an operator input transducer providing a first signal corresponding to a braking demand;

a rotatable vehicle member capable of having a rotation speed and an applied torque;

a torque feedback transducer assembly coupled to said rotatable vehicle member for measuring the torque and providing a second signal corresponding thereto;

a wheel speed sensor for providing a third signal corresponding to the rotation speed;

a controller for receiving signals including said first signal, said second signal, and said third signal and providing signals including a fourth signal, said fourth signal corresponding to an applied braking torque; and

a torque actuator assembly adapted to provide a substantially electrically distributed directly applied braking torque to said rotatable vehicle member in response to receiving said fourth signal from said controller;

wherein the torque actuator assembly is hydraulically independent from a master cylinder.

2. The system of claim 1, further including:

a second rotatable vehicle member;

a second torque feedback transducer assembly, said second torque feedback transducer assembly being associated with said second rotatable vehicle member and adapted to send a fifth signal to the controller;

a second wheel speed sensor, said second wheel speed sensor being associated with said second rotatable vehicle member and adapted to send a sixth signal to the controller; and

a second torque actuator assembly, said second torque actuator assembly being associated with said second rotatable vehicle member and adapted to supply an electrically distributed braking force to said associated rotatable vehicle member in response to receiving from said controller a seventh signal.

3. The system of claim 1 wherein the torque actuator comprises:

a hydraulic wheel cylinder having a unidirectional valve in fluid communication with said wheel cylinder;

a piston mounted at least partially within said wheel cylinder;

a piezoelectric element positioned within the hydraulic wheel cylinder and operationally coupled to said controller;

a rotatable brake element associated with said rotatable vehicle member; and

,

a non-rotatable brake element operationally connected to the piston and positioned between said rotatable brake element and said hydraulic wheel cylinder piston.

4. The system of claim 3 wherein the rotating vehicle member is a wheel, the non-rotatable brake element is a brake pad, and the rotatable brake element is a wheel rotor.

5. The system of claim 3 wherein the torque actuator further comprises a fluid reservoir in fluid communication with the unidirectional valve.

6. The system of claim 3 wherein the piezoelectric element comprises a flexible laminate of pre-stressed polymeric materials and piezoelectric ceramic.

11. The system of claim 1 wherein the controller comprises:

a digital controller;

at least one test circuit;

a power supply; and

an input/output interface.

12. The system of claim 11, wherein the digital controller is a real time embedded processor including an analog to digital converter, and control logic and test logic embedded in PROM.

13. The system of claim 12 wherein the digital controller further comprises at least one watchdog timer circuit adapted to coordinate fail-safe operation in the case of loss of operation of the controller.

14. The system of claim 12, further comprising:

a plurality of rotatable vehicle members;

a plurality of wheel speed sensors each individually associated with a separate rotatable vehicle member and operationally connected to the controller; and

a plurality of torque actuator assemblies each individually associated with a separate rotatable vehicle member and operationally connected to the controller, wherein the controller is adapted to individually control the plurality of torque actuator assemblies to provide brake torque to the plurality of rotatable vehicle members.

15. The system of claim 14, wherein the operator command input transducer, the wheel speed sensors, and the torque feedback transducers are adapted to provide input signals to the controller and wherein the controller is adapted to processing the input signals, to calculate a brake torque for each rotatable vehicle member, and to send commands to the torque actuator assemblies to individually brake the respective rotatable vehicle members.

16. The system of claim 11 further comprising an engine operation sensor operationally coupled to the vehicle and adapted to send a first signal to the controller when the vehicle is operating and a second signal to the controller when the vehicle is not operating.

17. The system of claim 16, wherein said controller applies a predetermined level of braking torque to the rotatable vehicle member when the first signal of the engine operation sensor is received, and removes the predetermined level of braking torque from the rotatable vehicle member when the second signal from the engine operation sensor is received.

7. A brake system for a vehicle, comprising:

an operator input transducer providing a first signal corresponding to a braking demand;

a rotatable vehicle member capable of having a rotation speed and an applied torque;

a torque feedback transducer assembly coupled to said rotatable vehicle member for measuring the torque and providing a second signal corresponding thereto;

a wheel speed sensor for providing a third signal corresponding to the rotation speed;

a controller for receiving signals including said first signal, said second signal, and said third signal and providing signals including a fourth signal, said fourth signal corresponding to an applied braking torque; and

a torque actuator assembly adapted to provide an applied braking torque to said rotatable vehicle member in response to receiving said fourth signal from said controller;

wherein the torque feedback transducer comprises;

a pair of overlapping torsion arms pivotably coupled to opposite sides of the torque actuator assembly and extending toward each other; and

a transducer element positioned between said torsion arms and operationally coupled to said controller;

wherein the plane of pivoting of said torsion arms is substantially perpendicular to the axis of rotation of the rotatable vehicle member.

8. The system of claim 7 wherein the transducer element is a flexible laminate of pre-stressed polymeric materials and piezoelectric ceramic.

9. The system of claim 8 wherein the operator command input transducer includes a foot pedal actuator adapted to provide proportional force feedback.

10. The system of claim 8 wherein the operator command input transducer includes a hand lever.

31. The system of claim 7, further including:

a second rotatable vehicle member;

a second torque feedback transducer assembly, said second torque feedback transducer assembly being associated with said second rotatable vehicle member and adapted to send a fifth signal to the controller;

a second wheel speed sensor, said second wheel speed sensor being associated with said second rotatable vehicle member and adapted to send a sixth signal to the controller; and

a second torque actuator assembly, said second torque actuator assembly being associated with said second rotatable vehicle member and adapted to supply a braking force to said associated rotatable vehicle member in response to receiving from said controller a seventh signal.

32. The system of claim 7 wherein the torque actuator comprises:

a hydraulic wheel cylinder having a unidirectional valve in fluid communication with said wheel cylinder;

a piston mounted at least partially within said wheel cylinder;

a piezoelectric element positioned within the hydraulic wheel cylinder and operationally coupled to said controller;

a rotatable brake element associated with said rotatable vehicle member; and

,

a non-rotatable brake element operationally connected to the piston and positioned between said rotatable brake element and said hydraulic wheel cylinder piston.

33. The system of claim 32 wherein the rotating vehicle member is a wheel, the non-rotatable brake element is a brake pad, and the rotatable brake element is a wheel rotor.

34. The system of claim 32 wherein the torque actuator further comprises a fluid reservoir in fluid communication with the unidirectional valve.

35. The system of claim 32 wherein the piezoelectric element comprises a flexible laminate of pre-stressed polymeric materials and piezoelectric ceramic.

18. A torque actuator control circuit comprising:

a digital controller having a timer circuit adapted to provide fail-safe operation in case of an emergency loss of the electronic controller;

a test circuit operationally coupled to the digital controller;

a power supply operationally coupled to the digital controller; and

an input/output interface adapted to receive a first input signal from a speed sensor, a second input signal from a torque sensor, and a third input signal from an input transducer and relay them to the digital controller and adapted to send a control output signal from the digital controller to a torque actuator;

wherein the digital controller is adapted to process signals from the input/output interface, determine the maximum level of torque required, and send a command signal through the input/output interface to the torque actuator.

19. A torque feedback transducer system comprising:

a frame;

a first torsion arm pivotably coupled at a first point of said first torsion arm to a first portion of the frame;

a second torsion arm pivotably coupled at a first point of said second torsion arm to a second portion of the frame;

said torsion arms including overlapping portions;

a piezoelectric transducer element positioned between said overlapping portions of said torsion arms and adapted to be operationally connected to a controller;

wherein said torsion arms pivot around their respective first points when a force is exerted on said frame, thereby compressing or decompressing said transducer element.

20. The system of claim 19, further comprising a linking member pivotably connected to said first torsion arm at a second point of said first torsion arm and pivotably connected to said second torsion arm at a second point of said second torsion arm.

21. The system of claim 20, wherein said linking member comprises a vehicle braking torque actuator.

22. The system of claim 19 wherein the transducer element is a flexible laminate of pre-stressed polymeric materials and piezoelectric ceramic.

23. A method for the independently controlled braking of each rotatable member of a vehicle, comprising:

a) providing a preprogrammed controller having predetermined vehicle and braking parameters;

b) providing a piezoelectrically induced torque actuator for each rotatable member, the torque actuators being adapted to apply a braking torque to their respective rotatable members;

c) providing a torque feedback transducer for each rotatable member, the torque feedback transducers being adapted to detect the developed brake torque on their respective individual rotatable members and to send a signal representing the brake torque to the controller;

d) providing a speed sensor for each rotatable member, the speed sensors being adapted to detect the rotational speed of their respective rotatable members and to send a signal representing the speed to the controller;

e) providing an operator input transducer adapted to send a signal representing a request for a level of braking torque to the controller;

f) determining a braking torque for each rotatable member in accordance with the request for a level of braking and within the predetermined braking parameters;

g) sending a signal to the torque actuator associated with each rotatable member representing the braking torque to be applied to the respective rotatable member; and

h) developing substantially the entire determined braking torque in the respective piezoelectrically induced torque actuator for each respective rotatable member.

24. The method of claim 23, wherein the predetermined braking parameters include a skid value, and further comprising the step of initiating an anti-lock protocol for a rotatable member when the speed sensor associated with that rotatable member detects a skid condition including a rotational speed less than the skid value.

25. The method of claim 24, wherein the step of initiating the anti-lock protocol includes the steps of:

calculating a μ

-slip curve from the inputs to the controller;

determining a level of torque for each rotatable member to correct the skid condition within the predetermined parameters;

applying the determined level of torque to each respective rotatable member to achieve a level of braking in accordance with the desired level of braking and within the predetermined braking parameters; and

maintaining the braking torque on the rotatable member at the level of torque within the predetermined.

26. The method of claim 25, wherein (a) further comprises providing a torque actuator including a flexible laminate of pre-stressed polymeric materials and piezoelectric ceramic positioned within an expandable and contractible bag positioned within a fluid-filled rotatable vehicle member cylinder.

29. The method of claim 23 further comprising:

providing an engine status sensor adapted to send a first engine status signal to the controller when the vehicle becomes inoperative and to send a second engine status signal to the controller when the vehicle becomes operative;

applying a predetermined level of braking torque to at least one wheel when the controller receives the first engine status signal; and

removing the predetermined level of braking torque from the wheels when the controller receives the second engine status signal.

30. The method of claim 23 further comprising:

providing an independent operator-controlled signal actuator operable to send an emergency brake signal having a duration;

applying a predetermined level of emergency braking torque to at least one wheel during the duration of the emergency brake signal; and

removing the predetermined level of emergency braking torque from the wheels after the duration of the emergency brake signal.

27. A method for the independently controlled braking of each rotatable member of a vehicle, comprising:

a) providing a preprogrammed controller having predetermined vehicle and braking parameters;

b) providing a piezoelectrically induced torque actuator for each rotatable member, the torque actuators being adapted to apply a braking torque to their respective rotatable members and;

c) providing a torque feedback transducer for each rotatable member, the torque feedback transducers being adapted to detect the developed brake torque on their respective individual rotatable members and to send a signal representing the brake torque to the controller;

d) providing a speed sensor for each rotatable member, the speed sensors being adapted to detect the rotational speed of their respective rotatable members and to send a signal representing the speed to the controller;

e) providing an operator input transducer adapted to send a signal representing a request for a level of braking torque to the controller;

f) determining a braking torque for each rotatable member in accordance with the request for a level of braking and within the predetermined braking parameters;

g) sending a signal to the torque actuator associated with each rotatable member representing the braking torque to be applied to the respective rotatable member; and

h) applying the determined braking torque to each respective rotatable member;

wherein (b) further comprises providing a pair of rotatable overlapping torsion arms fastened on opposite sides of the torque actuator and extending towards each other.

28. The method of claim 27, further comprising providing a flexible laminate of pre-stressed polymeric materials and piezoelectric ceramic positioned between the overlapping torsion arms.