Reducing Kinematic Error

A method for reducing kinematic error in a joint between distal and proximal portions of a manipulator, the joint having associated to it a motor for driving rotation thereof, a measurement device for measuring a rotation angle of the motor, a joint controller connected to the motor and to the measurement device for controlling at least the rotation angle of the motor based on input position commands, and a trajectory generator for outputting position commands, the method comprising:

• a. providing an acceleration sensor in the distal portion;
• b. selecting a trajectory to be followed by the acceleration sensor;
• c. estimating expected acceleration values to which the sensor is expected to be subject along said trajectory;
• d. outputting, by the trajectory generator, initial commands for moving the sensor along the trajectory;
• e. obtaining corrected commands by adding to a parameter specified in an initial command a kinematic error correction, and inputting corrected commands into the joint controller;
• f. recording acceleration values to which the sensor is subject while moving according to the corrected commands;
• g. judging whether a deviation between the expected acceleration values and the recorded acceleration values exceeds a predetermined threshold, and
• h. when the deviation is judged to exceed the threshold, modifying the kinematic error correction so as to reduce the deviation.