Counter-Rotating Motors with Linear Output

Abstract

An active suspension for a vehicle includes an actuator which incorporates a first rotary motor, a second rotary motor, and a transmission coupled to the first and second rotary motors to convert rotary motion to linear motion. A compensation force is determined to compensate for the rotary inertia of the system. A force feedback loop can be employed to reduce the error between the output force of the actuator and a force command supplied by an active suspension system controller.

1 . A suspension apparatus for coupling between a sprung mass and an unsprung mass of a vehicle comprising:
 a first rotary motor coupled to a support structure;   a second rotary motor coupled to the support structure, and;   a back drivable rotary-to-linear motion conversion mechanism having an output shaft, the rotary-to-linear motion conversion mechanism coupled to the first and second rotary motors,   a sensor having an output indicating movement of the rotary-to-linear motion conversion mechanism; and   a controller for receiving a force command, computing a compensation force based on a reflected inertia of the rotary-to-linear motion conversion mechanism and an acceleration derived from the sensor output, and computing a reflected inertia compensated force command from the force command and the compensation force to cause the first and second motors to produce the reflected inertia compensated force at the output shaft of the rotary-to-linear motion conversion mechanism.   
     
     
         2 . The suspension apparatus of  claim 1  wherein the support structure is coupled to the sprung mass of the vehicle and the output shaft of the rotary-to-linear motion conversion mechanism is coupled to the unsprung mass of the vehicle. 
     
     
         3 . The suspension apparatus of  claim 1  wherein the support structure is coupled to the unsprung mass of the vehicle and the output shaft of the rotary-to-linear motion conversion mechanism is coupled to the sprung mass of the vehicle. 
     
     
         4 . The suspension apparatus of  claim 1  wherein the output shaft of the rotary-to-linear motion conversion mechanism is selected from the group consisting of:
 a roller screw, a magnetic screw, a hydrostatic screw, a lead screw, and a tapered roller screw. 
 
     
     
         5 . The suspension apparatus of  claim 1  further comprising a passive suspension apparatus comprising a spring, wherein at least a portion of the active suspension apparatus is located inside the spring. 
     
     
         6 . The suspension apparatus of  claim 5  wherein the spring is a coil spring. 
     
     
         7 . The suspension apparatus of  claim 5  wherein the spring is a pneumatic spring. 
     
     
         8 . The suspension apparatus of  claim 1  further comprising:
 a sensor having an output indicative of a force output of the rotary-to-linear motion conversion mechanism; and 
 a controller for receiving a force command and the sensor output indicative of the force output of the rotary-to-linear motion conversion mechanism and in response to generate a modified force command for application to the first and second rotary motors, where the modified force command is based on a difference between the force command and the indicated force output. 
 
     
     
         9 . The suspension apparatus of  claim 1  further comprising:
 a first power amplifier coupled to drive at least the first rotary motor; and 
 control circuitry coupled to the movement sensor and the first power amplifier and configured to operate the power amplifier to drive the first and second rotary motors cooperatively based on a position indication of the movement sensor. 
 
     
     
         10 . The suspension apparatus of  claim 1  wherein the first and second rotary motors are configured to rotate in opposite directions to cause the output shaft to move in a single linear direction. 
     
     
         11 . A suspension apparatus for coupling between a sprung mass and an unsprung mass of a vehicle comprising:
 a first rotary motor coupled to a support structure;   a second rotary motor coupled to the support structure, and;   a back drivable rotary-to-linear motion conversion mechanism having an output shaft, the rotary-to-linear motion conversion mechanism coupled to the first and second rotary motors,   a sensor having an output indicative of a force output of the rotary-to-linear motion conversion mechanism; and   a controller for receiving a force command and the sensor output indicative of the force output of the rotary-to-linear motion conversion mechanism and in response to generate a modified force command for application to the first and second rotary motors, where the modified force command is based on a difference between the force command and the indicated force output   
     
     
         12 . The suspension apparatus of  claim 11  wherein the first and second rotary motors are configured to rotate in opposite directions to cause the output shaft to move in a single linear direction. 
     
     
         13 . A suspension apparatus for coupling between a sprung mass and an unsprung mass of a vehicle comprising:
 a first rotary motor coupled to a support structure;   a second rotary motor coupled to the support structure, and;   a back drivable rotary-to-linear motion conversion mechanism having an output shaft, the rotary-to-linear motion conversion mechanism coupled to the first and second rotary motors,   a sensor having an output indicating movement of the rotary-to-linear motion conversion mechanism,   a first power amplifier coupled to drive at least the first rotary motor; and   control circuitry coupled to the sensor and the first power amplifier and configured to operate the power amplifier to drive the first and second rotary motors cooperatively based on a position indication of the sensor.   
     
     
         14 . The suspension apparatus of  claim 13  wherein the first and second rotary motors are configured to rotate in opposite directions to cause the output shaft to move in a single linear direction.