Electric motor control strategies

• US 20060012321A1
• Filed: 07/16/2004
• Published: 01/19/2006
• Est. Priority Date: 07/16/2004
• Status: Active Grant

• Current Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Hamilton Sundstrand Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Rozman, Gregory I., Marks, Kenneth, Parsons, Douglas, Gustafson, James R.
• Granted Patent: US 7,332,884 B2
• Time in Patent Office: Days
• US Class Current: 318/432
• CPC Class Codes: F02C 7/275 Mechanical drives
• CPC Class Codes: F02N 11/0851 characterised by means for controlling the engagement or disengagement between engine and starter, e.g. meshing of pinion and engine gear
• CPC Class Codes: F02N 11/0859 specially adapted to the type of the starter motor or integrated into it
• CPC Class Codes: F02N 2011/0896 Inverters for electric machines, e.g. starter-generators
• CPC Class Codes: F02N 2200/041 Starter speed
• CPC Class Codes: F02N 2200/044 Starter current
• CPC Class Codes: F02N 2300/102 Control of the starter motor speed; Control of the engine speed during cranking
• CPC Class Codes: F02N 2300/104 Control of the starter motor torque

Abstract

An electric start system (20) includes a controller (40) that controls operation of a motor (22) used to start a device such as a gas turbine engine (24). In one example, the controller (40) determines when an acceleration rate of the motor (22) is outside of a desired range and dynamically controls the acceleration rate. In another example, the controller (40) determines when the motor (22) is disengaged from the engine (24) and controls a torque reference value to facilitate smoother reengagement. In another example, the controller (40) provides an initial starting torque value that allows for soft starting capabilities of the motor (22).

Claims

1. An electric start system, comprising

an electric motor adapted to be coupled to a device for starting the device;

and a controller that controls movement of the electric motor and performs at least one of;

(A) providing a starting torque signal for driving the motor during an initial start up of the device, the starting torque signal ramping up from a zero value to a selected value and remaining constant at the selected value until the controller determines that the motor has reached a chosen threshold speed;

(B) determining when an acceleration rate of the motor is outside of a selected range and automatically altering the acceleration rate; and

(C) determining when the motor is disengaged from the device and changing a motor torque reference signal from a present signal value corresponding to a present motor speed to a higher value.

2. The system of claim 1, wherein the device comprises a gas turbine engine and the motor is operably associated with the engine.

3. The system of claim 1, wherein the controller performs (A) and switches between square wave commutation and sinusoidal commutation, the controller performing (A) during the square wave commutation.

4. The system of claim 3, including a low-resolution position sensor that provides a square wave signal indicative of motor motion and wherein the controller uses the sensor square wave signal for the square wave commutation and as a basis for the sinusoidal commutation.

5. The system of claim 3, wherein the controller provides a torque reference signal responsive to a commanded motor speed during the sinusoidal commutation.

6. The system of claim 1, wherein the controller performs (A) and includes a starting torque integrator that provides the starting torque signal, the integrator receiving a first input for ramping up the starting torque signal and then receiving a second input when the motor has reached the chosen threshold speed such that the output of the integrator and the starting torque signal subsequently remain constant.

7. The system of claim 1, wherein the controller performs (B) and determines when the acceleration rate is outside of the selected range by determining a rate of change of a torque reference signal that is responsive to a commanded motor speed.

8. The system of claim 1, wherein the controller performs (B) and determines when the acceleration rate is outside of the selected range by determining a level of input power to the motor.

9. The system of claim 1, wherein the controller performs (C) and ramps up the torque reference signal value from the present value to the higher value.

10. The system of claim 1, wherein the controller performs (C) and increases the torque reference signal value toward a maximum value during reengagement of the motor with the device.

11. A method of controlling an electric motor in a electric start system where the motor is used to start a device, comprising at least one of:

(A) providing a starting torque signal for driving the motor during an initial start up of the device, the starting torque signal ramping up from a zero value to a selected value;

(B) determining when an acceleration rate of the motor is outside of a selected range and automatically altering the acceleration rate; and

(C) determining when the motor is disengaged from the device and changing a motor torque reference signal from a present signal value corresponding to a present motor speed to a higher value.

12. The method of claim 11, including performing step (A) and determining when the motor has reached a selected threshold speed and maintaining the starting torque signal at the selected value

13. The method of claim 11, including using square wave commutation during the start up and using sinusoidal commutation at higher motor speeds and including performing step (A) during the square wave commutation.

14. The method of claim 13, including providing a low resolution position sensor that provides a square wave signal indicative of motor motion and using the sensor square wave signal for the square wave commutation and for the sinusoidal commutation.

15. The method of claim 13, including providing a torque reference signal responsive to a commanded motor speed during the sinusoidal commutation.

16. The method of claim 11, including performing step (B) and determining when the acceleration rate is outside of the selected range by determining a rate of change of a torque reference signal that is responsive to a commanded motor speed.

17. The method of claim 11, including performing step (B) and determining when the acceleration rate is outside of the selected range by determining a level of input power to the motor.

18. The method of claim 11, including performing step (C) and ramping up the torque reference signal value from the present value to the higher value.

19. The method of claim 11, including performing step (C) and increasing the torque reference signal value toward a maximum value for reengaging the motor with the device.