A Joint Optimization Framework for Workspace Analysis of an Underactuated Hybrid Pose Adjustment Robot

Abstract Cable-driven parallel robots (CDPRs) are promising for construction automation owing to their large workspaces and high payload capacity. However, underactuated CDPRs (UACDPRs), which possess fewer cables than end-effector degrees-of-freedom, are generally underconstrained and suffer from issues such as pose ambiguity, discontinuous attitude transitions, and nonuniform cable force distributions. This article proposes a joint optimization framework for UACDPRs workspace analysis, applied to the hybrid pose adjustment (HyPA) robot, that simultaneously minimizes pose discontinuity and cable force variance. A system model that integrates the underactuated HyPA robot structure with horizontal motion platforms using Jacobian-based formulations is developed to enable accurate, offline workspace computation. Both simulations and hardware experiments validate the effectiveness of the method: the four-cable and five-cable actuated configurations show markedly reduced attitude differences (by up to 88.8%) and more uniform force distribution (fairness index up to 0.799), with a positioning error of 3.066 mm and force error of approximately 1.8% of the maximum tension. In contrast to conventional single-objective approaches, the proposed strategy offers a balanced solution and represents a step toward practical deployment of UACDPRs in construction automation, while highlighting the need for future work on real-time force redistribution and dynamic disturbance rejection to fully establish practical applicability.