Design Optimization and Active Disturbance Rejection Control of High-Precision Lightweight Linkage Robots with Flexible Joints

Lightweight linkage robots can reduce inertia and energy consumption in high-speed, high-precision manipulation, but reduced mass increases structural compliance and joint flexibility. Nonlinear stiffness, hysteresis, transmission error, and residual vibration can therefore degrade end-effector accuracy. This paper treats precision as a mechanical-control co-design problem, reviewing structural optimization, flexible-joint modeling, ADRC, disturbance observation, and learning-based compensation. Automotive suspension failures and Chinese recall statistics are then used as a reliability analogue. From 2021-2025, annual recall counts were relatively stable, whereas the number of affected vehicles varied markedly; design-related defects consistently accounted for about three-fifths of recalled vehicles. The evidence supports a design principle for lightweight robots: mass reduction should be constrained by fatigue life, stress concentration, manufacturing variability, and realistic dynamic loading, while robust control is used to reject disturbances and suppress vibration. Reliable high precision therefore depends on structurally robust lightweight design supported, rather than replaced, by advanced control.