Improvement of dynamic transparency of haptic devices by using spring balance

Force-reflecting devices should be static balanced to get good transparency. Generally counterweights are added to the haptic device to achieve a completely static balance in the working space. However this may decrease considerably the dynamic performance of the device due to larger inertia. This paper presents a mixed approach which uses counterweights to balance the orientation mechanism and springs to the position mechanism of the haptic interface. As an example a PHANTOM haptic device is applied. Simulation results show that the device could be balanced in a large enough space and the amount of imbalance is within 10 grams for all points within the working area while the inertia is decreased by more than ten percent. The dynamic performance of the device is thus well enhanced.