Forward kinematic model improvement of a spherical parallel manipulator using an extra sensor

•A method to improve the FKM calculation is proposed.•The use of extra sensor eliminates the effects of parallel singularity.•The improved FKM meets the real time constraints.•Experiments are carried and prove the benefits of the proposed approach.

In this paper an approach to improve the calculation of the forward kinematic model (FKM) of a spherical parallel manipulator (SPM) is presented and tested experimentally. This approach is based on adding an extra sensor on a passive joint. The measure of the passive joint angle reduces the complexity of the forward kinematic model and makes it possible for real time. The use of the extra sensor eliminates the effect of the parallel singularity on the FKM accuracy. An investigation is carried out to choose the position of the extra sensor that gives the better accuracy of the FKM. Experiments are carried out to prove the benefit of the redundant sensor on the FKM.