This paper deals with the design of multi-axis force (also known as force/torque) sensors, as considered within the framework of optimal design theory. Optimal design procedures consists of finding the combination of design variables that extremizes some optimality criterion: provided a suitable mathematical formulation of the problem, solutions can be efficiently obtained through currently available numerical techniques. The principal goal of this paper is to identify a mathematical objective function, whose minimization corresponds to the optimization of sensor accuracy. The methodology employed is derived from linear algebra and analysis of numerical stability. An objective function which can be applied to a large class of sensor configu...