Blended electrical/friction braking system with electric brake feedback monitor and method of use thereof

• US 6,441,573 B1
• Filed: 04/28/2000
• Issued: 08/27/2002
• Est. Priority Date: 04/28/2000
• Status: Expired due to Fees

• Current Assignee: Daimler Chrysler Company LLC (Stellantis NV)
• Original Assignee: Daimler Chrysler Company LLC (Stellantis NV)
• Inventors: Phillips, Robert W., Barbour, Theresa A., Ames, Richard P., Madden, William E. Jr., Chang, Steven T H, Langovsky, Nikola V., Zuber, Pierre A.
• Primary Examiner(s): Fletcher, Marlon T.
• Application Number:
  US09/560,493
• Time in Patent Office: 851 Days
• Field of Search: 318/611-612, 318/614-617, 318/87-88, 318/757, 318/759, 318/273, 318/362, 318/370-372, 318/375-376
• US Class Current: 318/375
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: B60L 7/26 Controlling the braking effect

Abstract

A blended electrical/friction braking system includes an electric brake feedback monitor which monitors a first signal corresponding to an electric brake effort request of an electric motor of an electrically powered vehicle. The electric brake feedback monitor detects one or more electrical conditions of the electric motor during electric braking and selectively supplies/terminates the first signal to/from a brake controller as a function of the first signal and the one or more electrical conditions. In response to termination of the first signal thereat, the brake controller causes a friction brake of the vehicle to assume the entire braking effort of the vehicle.

Claims

1. A blended electrical/friction braking system for use in a vehicle having an electric motor which can be operated to electrically brake one or more wheels of the vehicle and a friction brake for friction braking one or more wheels of the vehicle, the braking system comprising:

a brake controller for monitoring a brake effort request and for allotting the brake effort request between a first brake effort request corresponding to a desired amount of electrical braking effort to be supplied by the electric motor during electrical braking and a second brake effort request corresponding to a desired amount of friction braking effort to be supplied by the friction brake;

a drive control unit for producing from the first brake effort request a first signal corresponding thereto and for supplying the first signal to the brake controller;

at least one sensor for sensing at least one electrical condition of the electric motor during electric braking; and

a brake feedback monitor for monitoring the first signal, for converting the at least one sensed electrical condition into a second signal corresponding thereto, for comparing the first signal and the second signal and for terminating receipt of the first signal by the brake controller in response to a difference between the first signal and the second signal exceeding a predetermined difference, wherein the brake controller responds to the termination of the first signal thereat by allotting the incoming brake effort request entirely to the second brake effort request.

2. The braking system as set forth in claim 1, wherein the at least one sensed electrical condition includes voltage, current or the phase angle therebetween.

3. The braking system as set forth in claim 1, wherein:

the brake feedback monitor includes a processor and a relay connected to the processor to be controlled thereby;

the relay has a contact in a path of the first signal between the drive control unit and the brake controller; and

the processor controls the contact so that (i) the brake controller receives the first signal when the difference between the first signal and the second signal does not exceed the predetermined difference and (ii) the brake controller does not receive the first signal when the difference between the first signal and the second signal exceeds the predetermined difference.

4. The braking system as set forth in claim 1, wherein:

the brake feedback monitor includes a pair of relays connected in series in a path of the first signal between the drive control unit and the brake controller and a pair of processors each connected to control the contacts of the pair of relays and connected to sense the first signal on the path between the pair of relays and the brake controller;

one processor determines the second signal from the at least one sensed electrical condition and supplies the second signal to the other processor;

each processor determines whether the difference between the first signal and the second signal exceeds the predetermined difference; and

in response to determining the difference exceeds the predetermined difference, each processor signals one relay to change state thereby terminating receipt of the first signal by the brake controller.

5. The braking system as set forth in claim 4, wherein each relay includes a status output connected to one of the processors for supplying thereto an indication of the state of the contact of the relay.

6. The braking system as set forth in claim 5, wherein each processor signals the other relay to change state if the status output of the one relay does not indicate that the one relay is in a state that terminates receipt of the first signal by the brake controller.

7. The braking system as set forth in claim 4, wherein each processor, in response to detecting the first signal after signaling the one relay to change state, signals the other relay to change state.

8. The braking system as set forth in claim 1, wherein the first or second signal is a pulse width modulated signal.

9. A method of braking an electrical motor powered vehicle comprising the steps of:

(a) allotting a brake effort request between an electric brake effort request and a friction brake effort request;

(b) converting the electric brake effort request into a first signal;

(c) monitoring the first signal;

(d) monitoring one or more electrical conditions of the electric motor in response to the electric brake effort request;

(e) selectively opening and closing a feedback path for the first signal as a function of the first signal and the one or more electrical conditions; and

(f) in response to opening the feedback path, allotting the brake effort request entirely to the friction brake effort request.

10. The method as set forth in claim 9, wherein step (c) includes the steps of:

providing a pair of relays, each relay having a contact disposed in series with the feedback path;

signaling one relay to open its contact as a function of the first signal and the one or more electrical conditions; and

after signaling the one relay to open its contact and in response to detecting the presence of the first signal downstream in the feedback path from the one relay, signaling the other relay to open its contact.

11. The method as set forth in claim 9, wherein step (e) includes the steps of:

providing a pair of relays, each relay having a contact disposed in series with the feedback path and a status output which provides a status of the state of the contact thereof;

signaling one relay to open its contact as a function of the first signal and the one or more electrical conditions; and

after signaling the one relay to open its contact and in response to detecting from the status output of the one relay that its contact is closed, signaling the other relay to open its contact.

12. The method as set forth in claim 9, further including the steps of:

converting the one or more electrical conditions to a second signal;

determining a difference between the first signal and the second signal; and

closing the feedback path when the difference does not exceed a predetermined difference and opening the feedback path when the difference exceeds the predetermined difference.