Abstract In the early days,designer emphasized that human-like robotic hands should have high degree of freedoms(DOFs) and fully simulate all motions of human hands.It makes the system to be too expensive and complex. In recent years, the performance of grasp is no longer depend on the DOFs only after the concept of underactuated is applied. In this article, we discussed the designs and mechanisms of robotic hands and the design principle of underactuated. The SYS-1 underactuated human-like robotic hand uses only six actuator to control ten DOFs, the fingers of SYS-1 consist of underactuated six-bar linkage that simulate human¡¦s fingers motion. The ejection effect is also well controlled. Every finger is an independent module and can be separate or deploy according to the needs. The conduit-tendon system let SYS-1 can work in the water or high temperature environment without any damage. We also analysis the motion characteristic and grasp performance of SYS-1 and compare to the other similar designs.

Based on the traditional six-bar toggle mechanisms, this study is focused on the design of two types of cam-link mechanisms. Six-bar toggle mechanisms are simple, and they have an extreme mechanical advantage in toggle position so that they are widely used in plastic forming machines. Cam-crank-slider and cam-double-slider linkage are the two types mechanisms that we concerned. And we find the difference between these mechanisms for kinematic and dynamic performance. The benefit of cam-link mechanisms compares to linkage mechanisms is more precision points. We can synthesize the curve profile with the demand for forming acceleration or stroke. Because we need interpret the kinematic characteristic of toggle mechanisms by using several boundaries condition of different curves. This study selects two kinds from foregoing curve for the model.