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

A method for estimating angular errors of angle coders in a looped system including at least one actuator for rotating an axis and an angle coder providing a signal of position measurement of said axis, and including a calculation device for at least controlling said actuator, wherein the calculation device receives a setpoint signal at the system input, and the signal of position measurement 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 of rotation ωr assumed to be constant, have a spectrum consisting of the fundamental rotation frequency of value ωr and its harmonics kωr, k∈, the speed of rotation and the rotation frequency having a same unit, and wherein the calculating device calculates a command signal in a corrector, wherein,

• in a test phase, for a speed of rotation indexed j, ωrj, assumed to be constant, a specific corrector Cωrj(q) of said constant speed of rotation ωri is synthesized, said corrector Cωrj(q) being such that, for the frequency domain comprising the fundamental rotation frequency of value ωrj and a determined number of its first harmonics kωrj, k∈, 1<k≤Nl, Nl being the maximum rank of the harmonics to be considered, the corrector has a zero gain at these frequencies ωri, kωri, 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,
• wherein the test phase is repeated a determined number n of times with different setpoints of rotation at speed of rotation ωri each assumed to be constant, where, j∈, 1<j≤n,
• wherein the matrix relationships of the repeated test phases are concatenated in order to obtain an identifiable global matrix relationship, and
• wherein the parameters characterizing the coder errors and the torque undulations are estimated by solving the global matrix relationship, the corrector being synthesized either by a mixed-sensitivity method on an H-infinity control, or by a robust pole placement method on RST corrector.