As a new type of hydraulic system, the independent valve control system (IMCS) has higher flexibility compared with the traditional four-side slide valve control system. The independent metering control system (IMCS) is divided into four quadrant modes, based on the speed and load of the actuator. The traditional control methods always use a discrete control strategy to realize the switching between different modes based on mode recognition. However, the spool signals frequently switch, and the actuator operating pressure and speed are not stable when the IMCS is switched between different modes. To solve the above problems, this paper proposes a continuous control strategy for the IMCS. Based on the fuzzy control principle, the variable universe fuzzy controller (VUFC) was designed. The controller contains 49 fuzzy rules, and the output of the controller at any time is calculated by the weighted sum of several fuzzy rules. The VUFC divides the system into 49 rules, which are activated by multiple modes at any time to achieve a smooth transition between different modes. The VUFC was verified in a 37 ton excavator model and compared with the traditional independent metering meter-out (IM_MO) control strategy. The results showed that the VUFC significantly improved the frequent switching of the spool signals, and the running speed and pressure stability of the hydraulic cylinder were significantly improved. At the same time, the response speed of the hydraulic cylinder became faster at the start of the system. The VUFC can realize the continuous control of the IMCS and improve the operating performance of excavators.

In order to optimize the acceleration performance of a large inertia hydraulic actuator, this paper proposes a main valve input shaping control strategy, which makes the valve flow supply match the load-control demand by adjusting the main valve flow growth rate. Taking a load-independent flow distribution system as the research object, and aiming at the problems of large pressure overshoot, excessive overflow and oscillation tendency during the actuator acceleration process, this paper divides the acceleration process into the pressure build-up condition, the inertia-acceleration condition and the stable-flow regulation condition according to the change characteristics of the actuator driving pressure, and divides the main valve control signal into five stages to design the valve flow growth rate, thereby smoothing the driving pressure fluctuations by adjusting the actuator inertial load and mitigating the pressure release process. Based on the key structure-hydraulic parameters and test data of a 6-ton excavator, a virtual excavator that can accurately simulate the swing action and boom lifting action is built, and the software-in-the-loop test of the input-shaping control algorithm is carried out. The test results indicate that the proposed control strategy can effectively suppress the pressure overshoot, oscillation, and flow overmatching, thereby improving the dynamic stability and energy efficiency of the system.

Three-translation (3T) redundant actuated Delta/Par4-like manipulators with closed-loop units (CLU) are widely used in logistics sorting, industrial packaging, and other applications due to their superior load-carrying capacity and dynamic performance. However, compared to conventional 3T parallel mechanisms (PMs), there are fewer configurations of 3T redundant actuated PMs with CLU, and the existing CLU are of a single configuration. This paper introduces a method for synthesizing a 3T redundant actuated PM with CLU based on the atlas method. First, the degrees of freedom (DOF) line diagrams and constraint line diagrams of the moving platform are determined sequentially. By applying the dual rule, the constraint diagrams are decomposed, yielding six dual DOF spaces. The equivalent DOF line diagrams are expanded using the principle of line equivalence, which synthesizes a variety of novel 4- and 5-DOF branched chains with CLU. Second, considering the geometrically symmetric distribution criterion of the branched chains, two assembly schemes for redundant actuated 3T PMs with CLU are proposed, yielding at least 432 and 324 novel configurations, respectively. Finally, two representative novel mechanisms are selected, and their DOF properties are verified using screw theory, which demonstrates the feasibility and applicability of the synthesized method. This method systematically synthesizes novel redundant actuated 3T PMs with CLU, laying the foundation for further research into innovative CLU configurations.

This work systematically addresses the dual challenges of non-inertial dynamic coupling and kinematic constraint redundancy encountered in dynamic modeling of serial–parallel–serial hybrid robotic mechanisms, and proposes an improved Newton–Euler modeling method with constraint compensation. Taking the Skiing Simulation Platform with 6-DOF as the research mechanism, the inverse kinematic model of the closed-chain mechanism is established through $G_F$ set theory, with explicit analytical expressions derived for the motion parameters of limb mass centers. Introducing a principal inertial coordinate system into the dynamics equations, a recursive algorithm incorporating force/moment coupling terms is developed. Numerical simulations reveal a 9.25% periodic deviation in joint moments using conventional methods. Through analysis of the mechanism’s intrinsic properties, it is identified that the lack of angular momentum conservation constraints on the end-effector in non-inertial frames leads to system controllability degradation. Accordingly, a constraint compensation strategy is proposed: establishing linearly independent differential algebraic equations supplemented with momentum/angular momentum balance equations for the end platform. Co-Simulation results demonstrate that the optimized model reduces the maximum relative error of actuator joint moments to 0.98%, and maintains numerical stability across the entire configuration space. The constraint compensation framework provides a universal solution for dynamics modeling of complex closed-chain mechanisms, validated through applications in flight simulators and automotive driving simulators.