Abstract
We present a novel design method of a 6-axis Force/Torque (F/T) sensor with identical stiffness in all directions. In contrast to common F/T sensor designs, the proposed method is an analytical approach to the realization of a desired diagonal stiffness matrix which implies the complete decoupling of the stiffnesses in all directions. The first step of the design is to group the column vectors of a given rank 6 diagonal stiffness matrix into in-plane type and out-of-plane type stiffnesses. Each type of stiffnesses is then synthesized by means of three line vectors and designed as the corresponding serial-chain for a limb of an F/T sensor using only circular hinges. The F/T sensor can be formed by connecting the designed two serial-chains in series. However, for a practical design with minimum structural error and better strength, each of two type stiffnesses is further divided into a set of n separate serial-chains. Finally, the n-sets of serial-chains each consisting of six circular hinges that correspond in-plane and out-of-plane type stiffnesses are connected to the moving platform in parallel to complete the design. The FEM analysis and experiments are conducted to verify the proposed design method.
Highlights
Robots and robotic systems are widely used in a variety of fields, including manufacturing, health care, the military, and so on
A new geometric design method of an elastic 6-axis F/T sensor is presented that is an analytical approach to the realization of a desired diagonal stiffness matrix with the same stiffness in all directions
Any given 6 × 6 diagonal stiffness matrix with the prescribed linear and torsional stiffnesses is divided into rank 3 in-plane type and out-of-plane type stiffness matrices
Summary
Robots and robotic systems are widely used in a variety of fields, including manufacturing, health care, the military, and so on. As an increasing number of robots interact with or require direct contact with humans, it is important to ensure the control of robots is safe and precise. Researchers have been investigating force/torque (F/T) sensors suitable for measuring external forces or moments. The most common type of six-axis F/T sensor has a cross-beam structure. This type of sensor has an advantage of relatively simple design. It is difficult to obtain the positional information except the magnitude of force/moment, because it is commonly designed using numerical methods, but not an analytical method. It is difficult to ensure the same stiffness in every axial direction, which means the sensitivity is typically lower for lateral forces than in other directions. Complete decoupling of signals from each axis is difficult
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