A forward acceleration of the kinematic limbs for the redundant serial–parallel manipulators is studied. The relationships between the input velocity/acceleration and the output general velocity/acceleration of the kinematic limbs are discovered. The forward kinematic Jacobian matrices and the forward kinematic Hessian matrices are derived. A unified forward acceleration of the kinematic limbs is established for solving the output general acceleration of the kinematic limbs by only giving the input general velocity/acceleration of every parallel manipulator. A novel 2(RPS + SPR + UPS + SPU) type serial–parallel manipulator is constructed, several formulas are derived for solving the full forward general acceleration of the kinematic limbs in the redundant serial–parallel manipulator based on the unified forward acceleration model. The theoretical solutions are proved to be correct by the simulation solution of the novel serial–parallel manipulator.
A novel couple-constrained parallel wrist with three measuring force flexible fingers is designed for grabbing heavy objects and measuring grabbed forces. Its prototype is developed, its dynamics model is established, and its grabbing forces are measured. First, using the extended formulas of the skew-symmetric matrix, the kinematic formulas are derived for solving the Jacobian/Hessian matrices and the general velocity/acceleration of the moving links in the couple-constrained parallel wrist. Second, a dynamics model is established for solving the dynamic actuation forces, the couple-constrained forces, and the torque in the couple-constrained parallel wrist. Third, the theoretical solutions of the kinematics/dynamics of the couple-constrained parallel wrist are verified using a simulation mechanism. Finally, the grabbing forces of the three flexible fingers are measured and analyzed.
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