Abstract: To improve the quality of collaboration and interaction between human and robot, and lessen uncomfortable experience owing to the gravity and inertia of the mechanism itself, the parameter design method of robot is studied. A kind of 2-DOF virtual prototype is given as an example to demonstrate the method. Introducing the largest equivalent mass in the manipulating space to evaluate backdrivability of the mechanism, factors affecting performance of the mechanism are especially concerned. Kinematic isotropy is taken as a design target to optimize the kinematic parameters. Then taking gravity balance, backdrivability and dynamic isotropy into account, the dynamic parameter design criterion is provided. Finally the specification of the virtual prototype is concertly presented. The 2-DOF mechanism has good kinematic and dynamic isotropy in the middle part of workspace. But the gravity is not completely balanced, and the equivalent mass in the inner part of the workspace is very small, while still a little larger than expected in the outer part. Reasonable adjustment of masses、mass dis-tribution and kinetic lengths will lead to better gravity balance and backdrivality of the mechanism. The theory and method can be extended to the parameters design of other types of mechanism, which will emphasize the collaboration and inter-action quality especially gravity balance、backdri- vability and isotropy.

Key words: Backdrivability, Gravity balance, Isotropy, Robot