Adaptive servomotor control

• US 4,609,855 A
• Filed: 11/09/1984
• Issued: 09/02/1986
• Est. Priority Date: 11/09/1984
• Status: Expired due to Term

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Andrews, Nicholas W.
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): Keane, Patrick C.
• Application Number:
  US06/670,253
• Time in Patent Office: 662 Days
• Field of Search: 318/561, 318/611-616, 318/617-619, 318/609, 318/610, 318/620, 318/621, 364/157, 364/149, 364/148, 364/152, 364/162, 364/179
• US Class Current: 318/561
• CPC Class Codes: G05B 13/0245 not using a perturbation signal
• CPC Class Codes: G05B 2219/41028 Select gain with memory, rom table
• CPC Class Codes: G05B 2219/41086 Bang bang control
• CPC Class Codes: G05B 2219/42155 Model

Abstract

A servomotor controller provides high speed servomotor positioning be means of an on line adaptive state-feedback control algorithm. Servomotor position and velocity are the feedback states and each has an associated gain selected by means of a servomotor characterization scheme. The mechanical break frequency is used to select optimum gains and a high speed estimation technique is used to determine the mechanical break frequency. Position step change may also be used to select optimum gains. Gain tables are produced by an off-line simulation technique.

Claims

1. In a servomotor apparatus of the type comprising a servomotor, a servomotor controller and feedback means for providing feedback from said servomotor to said servomotor controller, the improvement comprising:

characterization means for periodically evaluating the equation;

##EQU18## where Wm is mechanical break frequency, θ

(t) is motor shaft position with time,

K_mv Ω

is the back EMF constant of the servomotor,

E is the voltage input to the servomotor, and

t is time; and

gain selection means for selecting one of a plurality of gain sets in response to said characterization of said servomotor, said selected gain set being supplied to said servomotor controller.

2. A servomotor apparatus comprising:

a servomotor;

means for selectively applying a drive voltage to said servomotor;

feedback means for providing indications of a shaft position and a shaft velocity of said servomotor;

characterization means for periodically evaluating the equation;

##EQU19## where W_m is mechanical break frequency, θ

(t) is motor shaft position with time,

K_mv Ω

is the back EMF constant of the servomotor,

E is the voltage input to the servomotor, and

t is time;

gain selection means for responding to said characterization means to select one of a plurality of gain sets; and

controller means for receiving said indications of servomotor shaft position and shaft velocity, said selected gain set and a desired servomotor shaft position and for controlling said means for selectively applying a drive voltage in response thereto.

3. A method of controlling a servomotor comprising the steps of:

monitoring a difference between an actual state of said servomotor and a desired state thereof;

estimating a mechanical break frequency of said servomotor by evaluating the equation;

##EQU20## where W_m is the mechanical break frequency, θ

(t) is motor shaft position with time,

K_mvΩ

is the back EMF constant of the servomotor,

E is the voltage input to the servomotor, and

t is time;

selecting a gain set from a plurality of gain sets responsive to said estimation of said mechanical break frequency;

applying said gain set to said difference between said desired and actual states of said servomotor;

determining a drive signal responsive to said application of said gain set to said difference; and

applying said drive signal to said servomotor.