A robot comprising: a base; an articulated arm extending distally of the base and including two arm members coupled by a joint; a motor; a gearbox having an input shaft coupled to an output of the motor and an output shaft configured to drive relative motion of the arm members about the joint; a position sensor configured to sense relative position of the arm members about the joint; and a control system coupled to the arm configured to drive the motor, the control system being arranged to perform a calibration operation to estimate torque loss in the gearbox by the steps of (i) estimating the inertia of the portion of the arm distal of the joint for motion about the joint; (ii) applying a determined drive power to the motor; (iii) receiving from the position sensor position data indicating the motion of the arm in response to the applied drive power; and (iv) estimating the torque loss in the gearbox in dependence on the estimated inertia, the determined drive power and the position data.

A method for reducing kinematic error in a joint includes providing an acceleration sensor; selecting a trajectory to be followed by the acceleration sensor; estimating expected acceleration values the sensor will experience along the trajectory; outputting initial commands for moving the sensor along the trajectory; obtaining corrected commands by adding to a parameter specified in an initial command a kinematic error correction and inputting the corrected commands into a joint controller; recording acceleration values to which the sensor is subject while moving according to the corrected commands; judging whether a deviation between the expected acceleration values and the recorded acceleration values exceeds a predetermined threshold, and when the deviation is judged to exceed the threshold, modifying the kinematic error correction so as to reduce the deviation.

A method includes providing a kinematic correction, outputting a first drive control signal specifying a motor speed having a first kinematic correction output based on a first parameter vector; extracting a frequency component and determining a first feedback vector; outputting to the motor a second drive control signal specifying a motor speed as a sum of the standard speed and a second kinematic correction output based on a second parameter vector; extracting a frequency component and determining a second feedback vector defining a second feedback amplitude and a second feedback phase; subtracting the first feedback vector from the second feedback vector to obtain a feedback difference vector; transforming the feedback difference vector into a difference; applying the transformation to the second feedback vector to obtain a third parameter vector; and programming the kinematic correction generator using the third parameter vector.

A method includes determining a movement of a robot arm in which a joint while being rotated from a start angle to an end angle, is subject to a constant gravity-induced torque; controlling execution of the movement, and, in the movement, controlling the joint to rotate from the start angle to the end angle at a constant speed; detecting speed fluctuations of the joint while it is being rotated from the start angle to the end angle; and estimating the kinematic error based on the speed fluctuations.

The present invention relates to an apparatus and to a method for compensation of errors of a numerically controlled machine tool, which has at least one controllable machine axis for relative positioning of at least one workpiece relative to one or more machining devices. The method comprises detecting actual measured values of at least one input variable describing a state of the machine tool by means of sensors on the machine tool, providing at least one compensation parameter to be utilized by a control device of the machine tool on the control device of the machine tool and compensating errors on the machine tool on the basis of the compensation parameter provided to the control device. The compensation comprises the compensation of thermal errors, the compensation of geometric errors and the compensation of errors on the basis of the dynamics of the machine.

An error compensation method for multi-axis parallel kinematics machine tools, including: building a theoretical Jacobian model of a multi-axis parallel machine tool to be compensated; and obtaining several geometric parameters of the theoretical Jacobian model and constructing a singularized geometric error model; constructing a singularized geometric error model with modeling error; solving the singularized geometric error model to obtain a singularized geometric error; substituting the singularized geometric error into the theoretical Jacobian model to construct a Jacobian model with correction term; generating a correction value of a motor of the multi-axis parallel machine tool to be compensated; calculating a corrected total displacement of the motor; substituting the corrected total displacement into an error prediction evaluation model to calculate predicted compensation errors under different geometric parameters; selecting a minimum predicted compensation error as a target compensation error. Thus improving the accuracy of error compensation for multi-axis parallel kinematics machine tools.