Method and Arrangement for Reducing the Torque Ripple of a DC Motor

• US 20170047872A1
• Filed: 04/23/2015
• Published: 02/16/2017
• Est. Priority Date: 04/23/2014
• Status: Active Grant

• Current Assignee: Kastanienbaum GmbH
• Original Assignee: Kastanienbaum GmbH
• Inventors: Spenninger, Andreas, Bhme, Niklas, Haddadin, Sami
• Granted Patent: US 10,069,447 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02P 21/22 Current control, e.g. using a current control loop
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: H02P 6/10 Arrangements for controlling torque ripple, e.g. providing reduced torque ripple

Abstract

The invention relates to a method and to an arrangement for reducing the torque ripple of a brushless DC motor (6) having a stator, a rotor, and a motor control unit, via which motor control unit the motor is controlled in a polyphase manner, having a data memory (1) for storing rotational angle-dependent correction data of the control current of the motor (6), which are impressed on the instantaneous values for controlling the motor. According to the invention, in a first step, for each position of the rotor, the phase currents holding the rotor in this position are determined and are used to derive reference current data, which is stored in a table of the data memory (19) together with the respective position data of the rotor, determined by the position sensor, and, in a second step, during continuous operation of the motor, the position-dependent reference current data stored in the data memory is combined with the control current of the motor. In a preferred refinement of the invention, the reference current data is conditioned in such a way that both outliers and noise are removed.

Claims

1. A method for reducing the torque ripple of a brushless DC motor with a stator, a rotor and a motor control unit by which the motor is controlled in a polyphase manner, with a data memory for storing correction data of the control current of the motor, which data is a function of the angle of rotation, in which correction data is impressed on the instantaneous values for controlling the motor, wherein

in a first step for each position of the rotor phase, currents holding the rotor in this position are determined from which reference current data is derived which is stored in a table of the data memory together with the particular position data of the rotor which is determined by a position sensor, and

in a second step during the running operation of the motor the position-dependent reference current data filed in the data memory is linked with the control current of the motor in such a manner that the original torque ripple of the motor is canceled or reduced.

2. The method according to claim 1, wherein the motor is a brushless DC motor which is controlled by a vector regulation, wherein the phase currents of the motor are generated by a performance electronic system as pulse-width-modulated voltages which are derived by an inverted Park transformation from a two-phase control current, and wherein the phase currents are returned in a feedback circuit via a Clark transformation and a Park transformation to the control current.

3. The method according to claim 2, wherein a position predictor regulator is provided by which the position-related impression of the reference current data read out of the data memory onto the control current is enabled to be varied as a function of the rotational speed of the rotor.

4. The method according to claim 1, wherein such data from the reference current data determined at each rotor position is eliminated which exceeds or drops below the given boundary limits.

5. The method according to claim 4, wherein

the reference current data is supported according to its median values,

a tunnel is formed around the determined median values over the entire detected range of rotational angles which runs at a fixed distance around the position-related median values,

that an average value is calculated from the reference current data located within the envelope, and

the values determined in this manner are stored as cleaned reference current values in the memory.

6. The method according to claim 1, wherein the brushless DC motor is used in articulations of a robot for compensating a torque ripple.

11. The arrangement according to claim 6, wherein the detection of the correction data takes place on a brushless DC motor to which a transmission is connected downstream and which is used in an articulation of a robot, wherein the correction data is detected as a function of the position of the motor and/or of the position of a transmission or other drive unit connected in downstream from the motor.

7. An arrangement for controlling a brushless DC motor for detecting and compensating a torque ripple of the motor with a stator and a rotor by a motor control unit with which the motor can be controlled in a polyphase manner, with a position sensor on the motor rotor for detecting the instantaneous relative or absolute position of the rotor, and with a data memory for storing rotational angle-dependent correction data of the control current of the motor which can be impressed on the instantaneous values for controlling the motor, wherein

at least two current sensors are provided for detecting the phase currents of the rotor,

the phase currents for controlling the motor can be determined in rotational angle-dependent positions of the rotor and can be stored as position-related reference current values in the data memory, and

the reference current values can be read out from the data memory in the running operation of the motor and can be impressed on the control current for controlling the motor.

8. The arrangement according to claim 7, wherein the motor control unit comprises a vector regulation which comprises the following:

a transmission module for converting the control current from a static 2-phase system to a rotating 2-phase system, a performance electronic system for the three-phase control of the rotor, a transformation module for converting the phase currents of the rotor into a rotating 2-phase system, and a transformation module for converting the rotating 2-phase system into a static 2-phase system whose current values are coupled back onto the control current.

9. The arrangement according to claim 8, wherein the performance electronic system comprises a module for the pulse width modulation and a circuit for amplifying the phase voltages of the rotor.

10. The arrangement according to claim 8, wherein the control current is guided via a position predictor regulator which determines a new position value from the rotor speed and the angular resolution of the position sensor, at which position value the reference current data of the original position is impressed during the running operation of the motor on the control current at a new position as a function of the instantaneous speed of the motor.