Publications

The basic idea of this article is the utilization of the multistable character of a compliant tensegrity structure to control the direction of motion of a crawling motion system. A crawling motion system basing on a two-dimensional tensegrity structure with multiple stable equilibrium states is considered. This system is in contact with a horizontal plane due to gravity. For a selected harmonic actuation of the system small oscillations around the given equilibrium state of the tensegrity structure occur and the corresponding uniaxial motion of the system is evaluated. A change of the equilibrium state of the tensegrity structure yields to novel configuration of the entire system. Moreover, the motion behavior of the novel configuration is totally different although the actuation strategy is not varied. In particular, the direction of motion changes. Therefore, this approach enables a uniaxial bidirectional crawling motion with a controllable direction of motion using only one actuato r with a selected excitation frequency.

This paper presents a new shape morphing compliant system - a shape morphing compliant structure with integrated actuators and sensors - for application as an adaptive soft robotic gripper. In many of today industries, there is a need to grasp differently shaped and sized objects as well as objects of a different stiffness or very soft objects. Classical rigid-body based grippers cannot safely manipulate such a wide variety of objects, as they are stiff and not adaptive. By integrating actuators within a compliant structure or mechanism, it is possible to develop an adaptive soft gripper that can achieve multiple shapes of its grasping surface i.e. different grasping patterns. Such gripper would be able to adapt its shape to different shaped objects and to realize safe grasping. By additionally integrating sensors, a compliant system results and the gripper can detect contact with objects. Via developed controller and actuators, appropriate shape morphing of its grasping surface can be realised. The concept of a two-finger gripper and a functional model of one gripper finger are presented in the paper. Actuators are formed by using shape memory alloy wire nitinol and sensors are formed by using conductive graphite foam. It will be shown that developed compliant system can realize an adaptive soft gripper finger with different grasping shapes. The control algorithm for the gripper finger is developed as well and it will be demonstrated that the gripper finger can decide which actuator needs to be activated in order to achieve appropriate shape morphing. The presented adaptive soft gripper structure can have many potential applications in robotics.