Effect on wrench-feasible workspace of cable-driven parallel robots by adding springs

•Springs are added between the end-effector and a base to modulate the workspace of Cable-Driven Parallel Robots (CDPRs).•Effects of different parameters of the spring on CDPR's wrenches are investigated.•An optimization is proposed to determine the desirable spring parameters.•Two numerical examples and a reshaped workspace validation experiment were conducted.•Springs with properly chosen parameters can affect the workspace of CDPRs without increasing the number of cables and motors.

Cable-driven parallel robots (CDPRs) possess a number of promising advantages over conventional rigid-link robots, such as light weight, large payload handling capacity, considerably large workspace, and simpler dynamics. However, since cables can only pull but not push its attachment point on the end-effector, it is usually challenging for the wrench-feasible workspace (WFW) of CDPRs to meet the design requirements. Therefore, redundant cables or load on the end-effector is used to attain the required workspace. In this paper, springs are added between the end-effector and a base with the goal to modulate the workspace. The effects of different parameters of the spring on CDPR's wrenches are investigated and an optimization is proposed to determine the feasible spring parameters. Workspaces of two planar and spatial examples are presented. A reshaped workspace validation experiment was conducted. These results show that springs, with properly chosen parameters, can increase or reshape the WFW of CDPRs to meet the specified design requirements.