Compliant Joints with Remote Centre of Compliance for the Improvement of the Motion Accuracy of a Gantry Stage

Gantry stages, which consist of two parallel acting servo drives, are commonly used in machine tools. One drawback of this concept is the crosstalk between both drives, when a stiff mechanical coupling is present. This can lead to a limited bandwidth of the position control or to high reaction forces. One way to overcome these issues is the usage of joints to create an additional degree of freedom, which allows the drives to move independently. The design of these joints as compliant elements offers advantages compared to common rolling bearings, such as low friction and the absence of backlash. Another benefit is the variability in the design of the compliant joints allowing for adjustments to the position of each joint’s centre of compliance. Thus, the position of the resulting pivot, and the transfer matrix between the motion of the drives and the motion at the gantry stage’s tool centre point, change as well. This paper addresses the placement of the joint’s centre of compliance in order to improve motion accuracy. For this purpose, joints with modular arranged compliant links have been designed. The characteristics of the joints and their effect on the behaviour of the gantry stage are compared using analytical investigations as well as experimental results.