Abstract: The six-dimensional force/torque sensor based on a Stewart parallel structure has great potential for application in the field of precise measurements of spatial forces, and it is a key issue in the structural design to develop a six-dimensional force/torque sensor with low coupling, high precision, ease of calibration and application. Traditional geometric parameters describing a Stewart parallel structure are six coupled variables, which are not beneficial to the decoupling of the design parameters to realize the design objective. In addition, the designed six-dimensional force/torque sensor is still coupled with isotropy in the condition of non-orthodology. This paper proposes to define and generate a Stewart parallel structure based on a circular hyperboloid of one sheet. By using this new definition, the geometric parameters describing a Stewart parallel structure is the minimal set only with three elements. The conditions of the forward isotropy and backward isotropy are derived based on the analytical static mathematical model, and the relationships are presented. The mathematical formulation of decoupled center is built. By compromising the performance indices, an optimal design routine is developed, and a new method is obtained to generate a class of isotropic six-dimensional force/torque sensor based on the Stewart parallel structure. The results provide a novel approach for the design of the six-dimensional force sensor.

Key words: Stewart parallel structures, isotropy, sensors, optimal design, circular hyperboloid of one sheet