Method for estimating angular errors of angle coders in precision rotary devices, device

A method for estimating angular errors of angle coders for a looped system including at least one actuator for rotating an axis and an angle coder a signal of position measurement of said axis, and including a calculation device for at least controlling said actuator, the calculation device receiving, on the one hand, a setpoint signal at the system input, and, on the other hand, the measurement signal, for looping the system, the rotation actuator generating torque undulations dm(t), the coder producing coder errors dc(t) which, for a setpoint signal yc(t) that corresponds to a rotation of the axis at a speed ωr supposed to be constant, have a spectrum consisted of the fundamental rotation frequency or and its harmonics kωr, kϵ, the calculating device calculating a command signal in a corrector, wherein,

• in a test phase, for a speed of rotation indexed j, θrj, supposed to be constant, a specific corrector Cθrj(q) of said constant speed of rotation θrj is synthesized, said corrector Cωrj(q) being such that, for the frequency domain comprising the fundamental frequency θrj and a determined number of its first harmonics kωrj, kϵ, 1<k≤Nl, the corrector having a substantially zero gain at theses frequencies ωrj, kωrj, which causes an opening of the loop at said frequencies, and a matrix relationship is established between the position measurements and a function of parameters characterizing the coder errors and the torque undulations, on the system with the specific corrector and at the constant speed of rotation ωrj,
• the test phase is repeated a determined number n of times with different setpoints of rotation at speed ωrj supposed constant, where, jϵ, 1<j≤n,
• the matrix relationships are concatenated in order to obtain an identifiable global matrix relationship,
• the parameters characterizing the coder errors and the torque undulations are estimated by solving the global matrix relationship.