Variable stiffness structural design of a dual-segment continuum manipulator with independent stiffness and angular position

This paper investigates the problem of the variable stiffness for a class of multisegment continuum manipulators. A simple design that mainly consists of two types of pneumatic muscle actuators (PMAs) is introduced to deal with the problem. To provide a detailed analysis, this characteristic of the variable stiffness is coupled with a mathematical analysis that is built upon the geometric mechanics and the performance testing of the stiffness in each PMA, thereby forming the stiffness model. Moreover, utilizing the simple design enables the continuum manipulator composed of two units to vary its stiffness independently from the angular position. In addition, using only the pressure variation of the PMAs in each unit, the dual-segment manipulator also has the capacity to implement independent unit locking. The experimental results further validate the expected performance of the proposed continuum manipulator.