Testing and speed control of electric motors in vehicles having

Details Testing and speed control of electric motors in vehicles having Testing and speed control of electric motors in vehicles having

1996-05-03

1998-09-22

Ip, Paul

Electricity: motive power systems

Braking

Plural, diverse or diversely controlled braking means

318434, 318371, 30312205, 30312207, 303 92, 340660, H02P 516, B60T 888, B60T 1316

Patent

active

058119477

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to the testing and speed control of pump and other electric motors used in vehicles having electronically controlled braking systems.
In the case, for example, of an anti-lock braking system, a pump driven by such a motor provides the hydraulic supply for the ABS system and it is therefore important that the facility be available for testing that the pump motor is operating, or operable, correctly. It is also desirable that the speed of the motor be known and be controllable.
Conventionally, actuation and control of the pump motor is achieved using an electromagnetic relay or electronic switch disposed on the "high side" of the motor, that is, amongst the circuitry connected to that side of the motor winding which is not connected directly to the vehicle chassis (ground). To test that the motor is "in-circuit" and operational, the relay is turned on temporarily. However, because the speed of operation of such a relay is relatively slow, the motor begins to run before the relay can be turned off again. This has a number of disadvantages, including higher noise and cost, inferior testability and pedal feel. Furthermore, the motor must deliver rated output at 8 volts supply, yet be capable of operating for long periods at 16 volts at the extremes of specified temperature.
Conventionally, ABS pump motors are not speed controlled because of the significant cost penalty associated with measuring the motor speed using a separate transducer. This cost limitation leads to high noise levels, inferior pedal feel and potential motor unreliability due to the wide voltage range over which the motor is likely to be operating.
It is therefore an objective of the present invention to provide an alternative means of testing and speed control for motors such as ABS pump motors which enable the aforementioned problems associated with the prior art to be reduced.
It is known from DE-3830164 that the rotational speed of a motor can be established electrically by making use of the fact that the residual magnetisation in the motor permits it to be operated as a generator for a short period of time which is sufficient for measurement. The current supply to the motor is interrupted at the instant of a current zero crossing and the voltage produced by the motor as a result of the residual magnetisation is monitored. The time period from the instant of the last zero crossing of the motor supply voltage to the first voltage zero crossing of the generated voltage is measured as a first time T.sub.1, and the time period from the instant of the first voltage zero crossing of the generated voltage to the second voltage zero crossing of the generated voltage is measured as a second time T.sub.2. The rotation speed of the motor is calculated using T.sub.1 and T.sub.2.
It is also known from WO-A-94/07717 that a value for the actual speed of a hydraulic pump, driven by an electric motor energised from a pulsed (interrupted) supply, can be established using only the voltage generated by the motor winding during the disconnection (off) periods.
In accordance with the present invention, there is provided a vehicle electrically controlled braking system having an electric motor connected between a source of voltage and ground and being controlled by opening and closing of a series electronic switch disposed on the "low side" of the motor between the motor and said ground characterised by, for establishing a value for the actual speed of rotation of the motor first means for measuring the supply voltage;
second means for measuring the e.m.f. generated by the motor during the disconnection periods of the supply; and
calculating means for subtracting the value obtained by the second means from that obtained from the first means to establish said value for the actual speed of rotation of the motor.
Preferably, said first means are adapted to measure the motor e.m.f. in said disconnection periods of the supply only after a delay to enable the back e.m.f caused by switching off the motor, to decay to a predetermined level

REFERENCES:
patent: 4744041 (1988-05-01), Strunk et al.
patent: 5372410 (1994-12-01), Miller et al.
patent: 5558409 (1996-09-01), Walenty et al.
patent: 5572100 (1996-11-01), Moulton

Affiliated with

Also associated with

Rating

Testing and speed control of electric motors in vehicles having does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Testing and speed control of electric motors in vehicles having , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Testing and speed control of electric motors in vehicles having will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1625520