Patent ID: 8013560

Claim:
A method for compensating for angular transmission error of an actuator provided with a motor and a wave gear drive, comprising: in a control system for positioning an output shaft of the actuator using a non-linear model composed of a mathematical model given by equations (1) through (3) to stipulate dynamic characteristics of a non-linear elastic deformation component included in the angular transmission error of the actuator and brought about by elastic deformation of a flexible externally-toothed gear of the wave gear drive: θ Hys ⁡ ( δ ) = { sgn ⁡ ( ω M ) ⁢ ( 2 ⁢ ⁢ θ def ⁢ g ⁡ ( ξ ) - θ Hys ′ ) : ⁢  δ  < θ r ⁢ ⁢ and ⁢ ⁢ ⁢  θ Hys  < θ def sgn ⁡ ( ω M ) ⁢ θ def : ⁢  δ  ≥ θ r ⁢ ⁢ or ⁢ ⁢ ⁢  θ Hys  ≥ θ def ( 1 ) g ⁡ ( ξ ) = { 1 2 - n ⁢ ( ξ n - 1 - ( n - 1 ) ⁢ ξ ) ⁢ : ⁢ n ≠ 2 ξ ⁡ ( 1 - ln ⁢ ⁢ ξ ) ⁢ : ⁢ n = 2 ( 2 ) δ =  θ M - δ 0  , ξ = δ / θ r ( 3 ) where θr: Width of unsteady region n: Constant representing the hysteresis bulge δ: Rotational distance after reversal of rotational direction θ′ Hys : Non-linear elastic deformation component θ Hys (δ) during reversal of rotational direction θ def : Direction-dependent deformation angle (offset component) δ 0 : Motor-shaft angle θ M during reversal of rotational direction; determining a non-linear elastic deformation component θ Hys during reversal of a motor-shaft rotational direction using the motor-shaft angle θ M and the non-linear model; adding a compensation input Nθ Hys (N: reduction ratio of the wave gear drive) to a motor-shaft angle command θ* M as feed-forward compensation, to thereby obtain a compensated motor-shaft angle command; and using the compensated motor-shaft angle command to control driving of the motor; whereby the non-linear elastic deformation component included in the angular transmission error of an output shaft of the actuator is compensated for.