ELECTRIC VEHICLE MOTOR TORQUE SAFETY MONITOR

• US 20150028785A1
• Filed: 07/23/2013
• Published: 01/29/2015
• Est. Priority Date: 07/23/2013
• Status: Active Grant

• Current Assignee: Atieva, Inc.
• Original Assignee: Atieva, Inc.
• Inventors: TANG, Yifan
• Granted Patent: US 10,447,195 B2
• Time in Patent Office: Days
• US Class Current: 318/434
• CPC Class Codes: B60L 15/20 for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 2240/421 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/429 Current
• CPC Class Codes: B60L 3/0061 relating to electrical machines
• CPC Class Codes: B60L 3/12 Recording operating variables ; Monitoring of operating variables
• CPC Class Codes: B60W 20/50 Control strategies for responding to system failures, e.g. for fault diagnosis, failsafe operation or limp mode
• CPC Class Codes: B60W 2050/0295 Inhibiting action of specific actuators or systems
• CPC Class Codes: B60W 2510/083 Torque
• CPC Class Codes: B60W 50/038 Limiting the input power, torque or speed
• CPC Class Codes: H02P 29/027 the fault being an over-current
• CPC Class Codes: H02P 29/032 Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A safety system for an electric motor controller is provided. The safety system includes a torque safety monitor having a first processor distinct from a second processor of a main motor controller. The first processor is configured to one of decrease or shut down AC (alternating current) power, sent from a DC/AC (direct current to alternating current) inverter to an electric motor, in response to an estimated torque of the electric motor differing from a commanded torque associated with the main motor controller by more than a set amount.

Claims

1. A safety system for an electric motor controller, comprising:

a torque safety monitor having a first processor distinct from a second processor of a main motor controller; and

the first processor configured to one of decrease or shut down AC (alternating current) power, sent from a DC/AC (direct current to alternating current) inverter to an electric motor, in response to an estimated torque of the electric motor differing from a commanded torque associated with the main motor controller by more than a set amount.

2. The safety system of claim 1, wherein the set amount is one from a set consisting of:

a fixed constant, a variable dependent upon motor speed, and a variable dependent upon vehicle speed.

3. The safety system of claim 1, further comprising:

a hardware protection unit electrically interposed between the main motor controller and the DC/AC inverter; and

the hardware protection unit configured to modify switching signals from the main motor controller, destined for the DC/AC inverter, in response to the first processor directing to decrease or shut down the AC power sent from the DC/AC inverter to the electric motor.

4. The safety system of claim 1, further comprising:

the first processor configured to receive a plurality of status parameters and to output system status information and a protection directive, the system status information and the protection directive based upon the plurality of status parameters.

5. The safety system of claim 1, wherein a predetermined delay is applied to the commanded torque, the predetermined delay compensating for a path delay of the estimated torque.

6. The safety system of claim 1, wherein the main motor controller and the torque safety monitor are configured to receive a first current measurement of the AC power from a first type of current sensor and the torque safety monitor is configured to receive a second current measurement of the AC power from a second current sensor.

7. The safety system of claim 1, further comprising:

the torque safety monitor configured to monitor at least one from a set consisting of;

an accelerator pedal, a brake pedal, a motor speed, and a stator current.

8. The safety system of claim 1, further comprising:

the first processor further configured to decrease a maximum commanded torque, as an output of the torque safety monitor, in response to the estimated torque of the electric motor differing from the commanded torque associated with the main motor controller by more than the set amount.

9. A safety system for a vehicle, comprising:

a torque safety monitor, distinct from a main motor controller of a vehicle;

the torque safety monitor including a torque estimator that produces an estimated torque from inputs including a measurement of a stator current of a motor and a rotational speed of the motor, the motor controlled by the main motor controller via the torque safety monitor;

the torque safety monitor including a torque monitor that performs a comparison of the estimated torque and a commanded torque, the commanded torque an input to the main motor controller; and

the torque safety monitor including a status and failure processor operable to output a protection directive based on the comparison of the estimated torque and the commanded torque, the protection directive acting to modify switching signals from the main motor controller to decrease AC (alternating current) power delivered to the motor.

10. The safety system of claim 9, further comprising:

a hardware protection unit coupled to the torque safety monitor and configured to couple to the main motor controller and a DC/AC (direct current to alternating current) inverter; and

the hardware protection unit having as inputs the switching signals from the main motor controller and having as outputs modified switching signals to the DC/AC inverter, the modified switching signals produced in accordance with the protection directive.

11. The safety system of claim 9, further comprising:

a hardware protection unit having a switching protection gate and a fault status processor;

the switching protection gate receiving the protection directive from the torque safety monitor and receiving a fault parameter from a DC/AC (direct current to alternating current) inverter;

the switching protection gate receiving the switching signals from the main motor controller and outputting modified switching signals to the DC/AC inverter;

the switching protection gate setting the modified switching signals equal to the switching signals in response to the fault parameter indicating no fault in the DC/AC inverter and the protection directive indicating agreement between the estimated torque and the commanded torque; and

the switching protection gate setting the modified switching signals to reduced power levels or an “

off”

state of the DC/AC inverter in response to the fault parameter indicating a fault in the DC/AC inverter or the protection directive indicating disagreement between the estimated torque and the commanded torque.

12. The safety system of claim 9, further comprising:

the torque safety monitor including a first monitor configured to receive a first sensor value from an accelerator pedal assembly and to detect a ground or power supply fault of the accelerator pedal assembly; and

the torque safety monitor including a second monitor configured to receive a second sensor value from a brake pedal assembly and to detect a ground or power supply fault of the brake pedal assembly.

13. The safety system of claim 9, further comprising:

the torque safety monitor including a third monitor configured to receive a vehicle speed value from a vehicle speed sensor and the rotational speed of the motor from a motor speed sensor and to detect a discrepancy therebetween exceeding a predetermined tolerance.

14. The safety system of claim 9, further comprising:

the torque safety monitor including a fourth monitor configured to receive a measurement of a stator current from a first current sensor and a measurement of the stator current from a second current sensor, the first current sensor and the second current sensor having differing types.

15. The safety system of claim 9, further comprising:

the torque safety monitor including a plurality of monitors coupled to the status and failure processor;

each monitor of the plurality of monitors receiving a sensed value relating to the motor or the vehicle and communicating a status to the status and failure processor; and

the status and failure processor further operable to output an aggregated status relating to a status of one or more of the plurality of monitors.

16. The safety system of claim 9, further comprising:

the torque monitor having a maximum commanded torque as an output;

the torque monitor producing a delayed commanded torque from the commanded torque;

the torque monitor setting the maximum commanded torque equal to a present value of the commanded torque in response to the estimated torque equaling the delayed commanded torque to within a specified amount; and

the torque monitor setting the maximum commanded torque equal to a lesser of the estimated torque and the present value of the commanded torque in response to the estimated torque differing from the delayed commanded torque by more than the specified amount.

17. A method of monitoring an electric motor, comprising:

comparing an estimated torque of an electric motor to a commanded torque; and

producing reduced power level switching signals, for a DC/AC (direct current to alternating current) inverter, from switching signals received from a main motor controller, in response to the estimated torque of the electric motor differing from the commanded torque by a preset amount.

18. The method of claim 17, further comprising:

producing a first measured value of a stator current of the electric motor from a first current sensor, for the main motor controller;

producing a second measured value of the stator current of the electric motor from a second current sensor; and

producing the estimated torque from the second measured value of the stator current of the electric motor and a measured value of a rotational speed of the electric motor.

19. The method of claim 17, further comprising:

detecting a ground or power supply fault in one from a set consisting of;

an accelerator pedal assembly, a brake pedal assembly, a vehicle speed sensor, and a motor rotational speed sensor; and

reporting the ground or power supply fault to a vehicle control unit.

20. The method of claim 17, further comprising:

detecting a first discrepancy between a vehicle speed and a motor speed;

detecting a second discrepancy between stator current measurements from a first sensor and a second sensor; and

reporting the first discrepancy or the second discrepancy to a vehicle control unit.