System and method for trajectory shaping for feasible motion commands

Patent metadata

Field	Value
Publication number	US-11716047-B2
Application number	US-202117352792-A
Country	US
Kind code	B2
Filing date	Jun 21, 2021
Priority date	Jun 21, 2021
Publication date	Aug 1, 2023
Grant date	Aug 1, 2023

Abstract

A system and method for shaping the trajectory of a motion command to reduce the effects of a load on performance of a motor dynamically modifies the motion profile in real time to limit the reference signals in the motion profile to feasible commands. A load observer determines an estimated disturbance acceleration. The estimated disturbance acceleration includes the dynamics of the controlled load and is used to modify a maximum and a minimum limit for the acceleration reference. The acceleration limits are, in turn, used to determine velocity limits. The motion profile and modified acceleration and velocity limits are provided to a state filter which determines a new motion profile for use by the motor drive to control operation of a motor and to control the load connected to the motor.

First claim

We claim:

1. A system for shaping a motion command for a motor,
the system comprising:
an input configured to receive a position feedback signal, wherein the position feedback signal corresponds to an angular position of the motor;
a memory configured to store a plurality of instructions; and
a processor in communication with the memory and configured to execute the plurality of instructions to:
sample the position feedback signal and determine an estimated value of a disturbance acceleration,
dynamically modify an acceleration limit in real-time responsive to the estimated value of the disturbance acceleration,
receive the motion command for the motor from a motion controller, wherein the motion command is a position reference signal, a velocity reference signal, an acceleration reference signal, or a combination thereof,
determine a modified motion command as a function of the motion command and the modified acceleration limit, wherein the modified motion command is a shaped position reference signal, a shaped velocity reference signal, a shaped velocity feedforward signal, a shaped acceleration reference signal, a shaped acceleration feedforward signal, or a combination thereof, and
provide the modified motion command as an input to a control module, wherein the control module is configured to control the motor.

2. The system of claim 1 wherein the processor is further configured to dynamically modify the acceleration limit by:
reading an initial acceleration limit value from the memory, and
adding the estimated value of the disturbance acceleration to the initial acceleration limit value.

3. The system of claim 2 wherein:
the motion command includes the position reference signal and the velocity reference signal,
the processor is further configured to dynamically modify a velocity limit in real-time, and
the modified motion command includes the shaped position reference signal and the shaped velocity reference signal.

4. The system of claim 3 wherein the processor is further configured to:
determine a position error by determining a difference between the position reference signal and the shaped position reference signal,
determine a velocity error by determining a difference between the velocity reference signal and the shaped velocity reference signal,
determine a modified position error by subtracting a deceleration correction value from the position error, and
determine an intercept time by dividing the velocity error by the modified position error.

5. The system of claim 4 wherein the processor is further configured to dynamically modify the velocity limit by:
multiplying the modified acceleration limit with the intercept time, and
adding a resultant value from multiplying the modified acceleration limit with the intercept time to the velocity reference signal.

6. The system of claim 1 wherein the processor is further configured to:
execute a control module to regulate a current output to the motor, and
execute a state filter in parallel to executing the control module, wherein:
the state filter includes a model of the control module,
the state filter receives the motion command and the dynamically modified acceleration limit as inputs, and
the state filter determines the modified motion command as an output.

7. The system of claim 1 wherein:
the processor is further configured to dynamically modify a velocity limit,
the state filter receives the dynamically modified velocity limit as an input,
the motion command includes the position reference signal, the velocity reference signal, and the acceleration reference signal, and the modified motion command signal includes the shaped position reference signal, the shaped velocity reference signal, and the shaped acceleration reference signal.

8. A method for shaping a motion command for a motor,
the method comprising the steps of receiving at a motor drive the motion command for the motor from a motion controller, wherein the motion command is a position reference signal, a velocity reference signal, an acceleration reference signal, or a combination thereof;
sampling with the motor drive a position feedback signal corresponding to an angular position of the motor;
determining in the motor drive an estimated value of a disturbance acceleration;
dynamically modifying an acceleration limit in real-time responsive to determining the estimated value of the disturbance acceleration; and
determining a modified motion command as a function of the motion command and of the modified acceleration limit, wherein the modified motion command is a shaped position reference signal, a shaped velocity reference signal, a shaped velocity feedforward signal, a shaped acceleration reference signal, a shaped acceleration feedforward signal, or a combination thereof.

9. The method of claim 8 wherein the step of dynamically modifying the acceleration limit further comprises the steps of:
reading an initial acceleration limit value from a memory of the motor drive, and
adding the estimated value of the disturbance acceleration to the initial acceleration limit value.

10. The method of claim 9 wherein:
the motion command includes the position reference signal and the velocity reference signal,
the method further comprises the step of dynamically modifying a velocity limit in real-time, and
the modified motion command includes the shaped position reference signal and the shaped velocity reference signal.

11. The method of claim 10 further comprising the steps of:
determining a position error as a difference between the position reference signal and the shaped position reference signal,
determining a velocity error as a difference between the velocity reference signal and the shaped velocity reference signal,
determining a modified position error by subtracting a deceleration correction value from the position error, and
determining an intercept time by dividing the velocity error by the modified position error.

12. The method of claim 11 wherein the step of dynamically modifying the velocity limit further comprises the steps of:
multiplying the modified acceleration limit with the intercept time, and
adding a resultant value from multiplying the modified acceleration limit with the intercept time to the velocity reference signal.

13. The method of claim 8 further comprising the steps of:
executing a control module to regulate a current output to the motor, and
executing a state filter in parallel to executing the control module, wherein:
the state filter includes a model of the control module,
the state filter receives the motion command and the dynamically modified acceleration limit as inputs, and
the state filter determines the modified motion command as an output.

14. The method of claim 8 further comprising the step of dynamically modifying a velocity limit in real-time, wherein:
the motion command includes the position reference signal, the velocity reference signal, and the acceleration reference signal,
the modified motion command is further determined as a function of the modified velocity limit, and
the modified motion command signal includes the shaped position reference signal, the shaped velocity reference signal, and the shaped acceleration reference signal.

15. A system for shaping a motion command, the system comprising:
a memory configured to store a plurality of instructions; and
a processor in communication with the memory and configured to execute the plurality of instructions to:
obtain an estimated value of a disturbance acceleration, wherein the disturbance accel

Assignees

• Rockwell Automation Tech Inc

Inventors

• Hoffman Jonathan D
• Fast Brian
• Miklosovic Robert J

Classifications

• H02P29/024 Primary

  Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load · CPC title

• H02P29/10

  for preventing overspeed or under speed · CPC title

• H02P29/40

  Regulating or controlling the amount of current drawn or delivered by the motor for controlling the mechanical load · CPC title

• H02P6/08 Primary

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

• H02P23/20 Primary

  Controlling the acceleration or deceleration · CPC title