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

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 non-uniform cable force distributions. This paper 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 designed for accurate workspace computation. Both simulations and hardware experiments validate the effectiveness of the method: the 4-cable and 5-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 towards 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.