Electric motor apparatus

Patent metadata

Field	Value
Publication number	US-2020366223-A1
Application number	US-202015931774-A
Country	US
Kind code	A1
Filing date	May 14, 2020
Priority date	May 15, 2019
Publication date	Nov 19, 2020
Grant date	—

Abstract

An electric motor apparatus having a controller and a torque demand signal modifier. The controller may produce a set signals to a drive stage of the motor where the drive stage applies a voltage to each phase of the motor to cause currents to flow in each phase of the motor corresponding to a current demand signal fed into the controller. The torque demand signal modifier may receive a target torque demand signal representative of a target torque demanded from the motor and outputs an actual torque demand signal which is converted into the current demand signal that is fed to the controller. The actual torque demand increases in value as a function of time towards the target torque demand value following a predefined ramp selected to ensure that the maximum current gradient of the current demand does not exceed a predetermined limit.

First claim

What is claimed is:

1 . An electric motor apparatus for controlling an electric motor supplied by a source, such as a battery or a dc/dc converter, in which the electric motor apparatus comprises:
a controller arranged to produce as an output a set signals that are fed to a drive stage of the motor, in which the drive stage is arranged to apply a voltage to each phase of the motor to cause currents to flow in each phase of the motor corresponding to a current demand signal fed into the controller, a torque demand signal modifier that receives as an input a target torque demand signal representative of a target torque demanded from the motor and outputs an actual torque demand signal that is converted into the current demand signal that is fed to the controller, the actual torque demand increasing in value as a function of time towards the target torque demand value following a predefined ramp selected to ensure that the maximum current gradient of the current demand does not exceed a predetermined limit when the voltage supplied by the battery is at a nominal value corresponding to the battery being fully charged, wherein the torque demand signal modifier is arranged to modify the predefined ramp as a function of the battery voltage such that the maximum current gradient generated matches a predefined current gradient limit value.

2 . An electric motor apparatus according to claim 1 in which the torque demand signal modifier modifies the ramp such that at lower battery voltages the rate of increase of torque demand towards the target at all points along the ramp is boosted compared with a higher battery voltage.

3 . An electric motor apparatus according to claim 1 in which the predefined increases the demanded motor torque from zero voltage to a maximum target voltage equal to the battery voltage so that the gradient at the final part of the ramp matches the predetermined gradient limit.

4 . An electric motor apparatus according to claim 1 wherein the ramp is boosted when the battery source voltage is lower than the nominal battery voltage.

5 . An electric motor apparatus according to claim 4 which boosts the ramp by multiplying the ramp by a scaling factor.

6 . An electric motor apparatus according to claim 1 wherein the torque demand signal modifier generates one or more of the current limits as a function of the battery terminal voltage.

7 . An electric motor apparatus according claim 1 wherein the torque demand signal modifier determines a torque demand gradient using a model of the motor that includes a plurality of motor parameters which combine at least two or more of: a motor stator equivalent resistance, a motor temperature, a motor mechanical velocity, a motor torque constant, a motor maximum bridge power, and a motor bridge equivalent resistance.

8 . An electric motor apparatus according to claim 1 wherein the torque demand signal modifier sets limits for the torque demand gradient based on the battery voltage and a model of the motor parameters that relates the torque to the motor current for a given motor operating condition.

9 . An electric motor apparatus according to claim 1 further comprising a current monitor which monitors the actual current demand values from the current controller, or the motor actual current value, or calculates estimates of the current value, and determines an actual current gradient from those values and in the event that the value exceeds the current gradient limit the torque demand gradient limiter is arranged to reduce the amount of boost of the ramp that is applied.

10 . An electric motor apparatus according to claim 9 in which the current monitor monitors the actual current values or estimated current values or current demand gradients as part of a feedback control loop so that the torque demand limits are driven to the optimum values to limit the currents drawn from or fed into the battery.

11 . A method of controlling an electric motor apparatus of the kind comprising an electric motor and a control circuit, the motor and control circuit being supplied by a battery source, the method comprising the steps of:
receiving a target torque demand signal representative of a target torque demanded from the motor; generating an actual torque demand signal that increases in value as a function of time towards the target torque demand value following a predefined ramp selected to ensure that the maximum current gradient does not exceed a predetermined limit when the voltage supplied by the battery is at a nominal value corresponding to the battery being fully charged; producing a set of motor current demand signals from the actual torque demand signal; applying a voltage to each phase of the motor to cause currents to flow in each phase of the motor corresponding to the current demand signals; and modifying the predefined ramp as a function of the battery voltage such that the maximum current gradient generated matches a predefined current gradient limit value.

Assignees

• Zf Automotive Uk Ltd

Inventors

• Coroban-Schramel Vasile

Classifications

• H02P6/08

  Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence) · CPC title

• H02P25/18

  with arrangements for switching the windings, e.g. with mechanical switches or relays · CPC title

• H02P27/085 Primary

  wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency · CPC title

• H02J7/14

  for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle · CPC title

• B62D5/046 Primary

  Controlling the motor · CPC title