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A novel root based optimization algorithm (ROA), which mimics the proliferation of plant roots, is proposed to evaluate the performances of a multi-axial road test rig over a prescribed workspace. Plant roots have developed complex behavior patterns to search for nutrients in the soil and even exhibit swarm intelligence. The growing roots can adapt their actions such as elongation, branching, and tropistic movement according to the environment. During the process of foraging for water and nutrients, the adaptive growth behavior of roots can be simulated to tackle the optimization problem. The efficiency of the proposed ROA has been validated by comparing it with well-known intelligent algorithms using classical and IEEE CEC 2019 benchmark functions. Computational results indicate that ROA outperforms other algorithms to search a global optimum on several benchmarks. Furthermore, the results are tested with nonparametric statistical methods, e.g., Wilcoxon rank-sum test. Besides, ROA is applied to the optimal dimensioning synthesis of the multi-axial road test rig (MRTR) based on the orthogonal 6-RSS parallel manipulator to promote the device's performance. The inverse kinematics of the multi-axial road test rig based on the asymmetrical orthogonal 6-RSS parallel mechanism is analyzed in detail. Applying the achieved dimensionless Jacobian, the performance criteria involving the global isotropy index, the force/velocity transmissibility index, the decoupling index are established. By simultaneously taking account the proposed criteria of performance, structural optimization is carried out resorting to ROA. Finally, a set of optimized dimensional parameters is obtained. The practical application further illustrates that ROA has the potential to deal with complex optimization problems.

Most interaction control formulations focused on electrically driven parallel mechanism. In this paper, the combining practice applications of compliant motion control technique on six degrees of freedom (6-DOF) hydraulic parallel mechanism (HPM) are investigated. According to the manipulation task specification and hydraulic control system characteristics, three different compliant motion control schemes are presented in three typical application scenarios, respectively: a parallel position/force control scheme in the joint space coordinate for train curve negotiation performance test, a hybrid position/force control scheme with the internal force suppression for shaking table with actuation redundancy, and a hybrid impedance control scheme for auto-docking mechanism based on force and vision. The feasibility and effectiveness of the proposed schemes were verified through a series of experiments. It showed that the 6-DOF HPM achieves good compliant behavior by applying the proposed compliant motion control techniques. These schemes could also be extended to other applications where the compliant motion of the 6-DOF HPM is required.

The iterative learning control (ILC) based on the linear frequency-domain model has been employed to replicate the road conditions for the vehicle durability testing in the laboratory. Generally, the vehicle and the multi-axial hydraulic test rig behave strong nonlinearities, which requires a large number of iterations to correct the tracking error. Hence, the process of drive file (i.e., the input signals which drive the actuators of the test rig) generation is time-lengthy and tedious. A method that combines the ILC with the Quasi-Newton algorithm over the complex space (QNILC) is developed to speed up the drive file construction for the multi-axial vibration test rig. The impedance matrix can be updated with Broyden’s method to reduce the modeling errors and make the iteration more robust. An auxiliary estimating loop is inserted into the iteration process to attain an optimal learning gain. The convergence of the proposed method has been proven to be monotonic. This approach is validated through simulation, where the target signals are the real-life spindle forces gathered from the wheel force transducer. The simulation results demonstrate that the QNILC can improve the convergence rate and increase the tracking accuracy than the current offline ILC. The QNILC reduces the iteration number from nine down to five to converge to the desirable index compared with the offline ILC using gain 0.5. The new method based on the optimization algorithm can extend to other repetitive tracking processes.

For simulating the shock wave with high peak force in a short duration, a novel variable damping hydraulic shock wave simulator was developed, and it was used for simulating the cannon recoil motion. The working principle of this simulator was explained with the assistance of established mathematical model and the flow behavior in damping channel was analyzed. The shock wave characteristics curves were obtained by using the numerical computation method. The results showed that the shock wave characteristics were directly related to the sectional area of the damping channel and the damping fluid medium characteristic; the shock wave curve can be simulated by adjusting the variable damping parameters. The computational results agreed well with the theory analysis, which meant that the proposed mathematical model can be used for supplying theoretical references for the cannon recoil motion in artillery fire shock simulation test.

Service load replication performed on multiaxial hydraulic test rigs has been widely applied in automotive engineering for durability testing in laboratory. The frequency-domain off-line iterative learning control is used to generate the desired drive file, i.e. the input signals which drive the actuators of the test rig. During the iterations an experimentally identified linear frequency-domain system model is used. As the durability test rig and the specimen under test have a strong nonlinear behavior, a large number of iterations are needed to generate the drive file. This process will cause premature deterioration to the specimen unavoidably. In order to accelerate drive file construction, a method embedding complex conjugate gradient algorithm into the conventional off-line iterative learning control is proposed to reproduce the loading conditions. The basic principle and monotone convergence of the method is presented. The drive signal is updated according to the complex conjugate gradient and the optimal learning gain. An optimal learning gain can be obtained by an estimate loop. Finally, simulations are carried out based on the identified parameter model of a real spindle-coupled multiaxial test rig. With real-life spindle forces from the wheel force transducer in the proving ground test to be replicated, the simulation results indicate that the proposed conventional off-line iterative learning control with complex conjugate gradient algorithm allows generation of drive file more rapidly and precisely compared with the state-of-the-art off-line iterative learning control. Few have been done about the proposed method before. The new method is not limited to the durability testing and can be extended to other systems where repetitive tracking task is required.

In order to promote the research and development on evaluating the seismic performance of structures, China State Construction Engineering Corporation (CSCEC) planned to construct a large-scale loa...

Experimental generation of high-power impact environments is a long-term problem filled with significant difficulty. The reliability and reproduction of these high-power impact levels in a controlled setting is complicated and important. The high-power impact loads simulation test has proven to be an appropriate tool for this application, which can simulate the large-caliber gun recoil process without the use of firing practice. The impact test system uses high-precision, computer-controlled hydraulic actuators to fire a piston mounted with the impact programmer at high velocities into the large-caliber gun muzzle. In the developed experimental series, the shock acceleration, recoil velocity and displacement waves are received. The results are used to display the capabilities of the impact simulation test to induce a wide range of shocks on the large-caliber gun and display the effectiveness of the device as a shock loading tool which simulates the large-caliber gun recoil motion.

The wheel coupling road simulation system can simulate the vibration environment of the vehicle and its key components under the actual road conditions. In vibration control, the result of FRF identification directly affects the quality of control. This paper adopted a modified non-parametric identification method to identify the FRF of the system. Moreover, uses the coherent function to evaluate FRF indentified and RPC algorithm to verify control precision. The simulation design is given blow.

In order to test vehicle shift-feel, establish key models of automotive power transmission such as automotive engines, torque converters, transmissions, clutches, and vehicle loads. Build up the simulink model of the whole vehicle power transmission system, simulate the vehicle accelerates, observe the variety of the speed of the Turbine speed of hydraulic torque converter and the output shaft torque.

To improve tracking and synchronization control precision of electro-hydraulic shaking tables system, this paper presents a novel adaptive reaching law sliding mode controller (ARLSMC) for double shaking tables system with parameter uncertainty and disturbance. The ARLSMC combined a sliding mode controller based on a novel adaptive reaching law to improve dynamic performance with an adaptive controller to estimate the uncertain parameters online in order to reduce the system chattering. Besides, the proposed ARLSMC is introduced into the cross-coupled controller of double shaking tables. The stability of the control system is analyzed applying Lyapunov theory, and it is proven that both the tracking errors and synchronization error can converge to zero in finite time. The co-simulation model is built using MATLAB/Simulink and Adams for verification of the proposed control strategy. Various simulation tests are performed and simulation results demonstrate that the proposed method has a fast dynamic response performance, high control precision, and strong robustness.

Adaptive inverse control (AIC) is an advanced control technology which can efficiently learn and control the severely nonlinear and real-time plant, such as the electrohydraulic shaking table (EST). The foundation of AIC is the system identification of the plant via an adaptive filer. The traditional adaptive filter theory is known as a fixed tap-length (length of the weight vector) FIR (Finite impulse response) filter whose weights change by adaptive algorithm automatically. The mismatch between plant and the fixed tap-length will cause inaccuracy or compute complexity. This paper introduce a variable tap-length NLMS(VTLNLMS) algorithm to find the optimum tap-length (OPTL) of the model of multi-DOF EST, then use AIC to improve the accuracy of time wave replication. The dynamics response nonlinear model of the EST is built to reflect the experimental situation. The nonlinear EST model and referred algorithm are simulated in MATLAB/Simulink. Results show the AIC with OPTL is effective in the EST.

This paper introduces the improved measures of Electromagnetic Compatibility (EMC) for Automatic Transmission Control Module (TCM) circuit design. The improved electromagnetic designs for TCM circuit can be divided into two aspects, which are Electromagnetic Interference (EMI) and Electromagnetic Susceptibility (EMS). The EMI characteristics are obtained by measuring the TCM. Through analyzing the source and principles of electromagnetic noise, the improved circuits are designed to depress the EMI emissions depending on the characteristics of EMI noise and EMC standards. For EMS, the protection measures are used to protect the TCM basing on the parameters and effects of EMS test. And research method integrated computer simulation and experiment has been used in this paper. The PSPICE circuit simulation software provides guide for improving the design of TCM circuits. After debugging the actual improved circuits and adjusting the circuits' parameters, then the improved circuits are really used in the TCM. And the improved TCM can satisfy the EMC standards.

In order to improve the accuracy performance of a six degree-of-freedom (DOF) redundantly actuated parallel mechanism (RAPM), a self-calibration method based on sensor redundancy is presented. The kinematic model of the RAPM is built and its 44 identifiable parameters are determined by QR decomposition of the identification matrix. Consequently, the self-calibration algorithm is formulated and the least-squares method is used to correct kinematic parameters. A guideline for selection of measurement configurations is presented. Numerical simulations are performed to confirm the validity of the proposed calibration algorithm. Simulation results show that the average parameter error of 2.23 mm is reduced to 0.12 mm, and the position and orientation accuracy of the platform can reach 0.05 mm and 0.16 mrad after calibration.

A digital controller based on DSP was proposed for electrohydraulic motion simulator. This digital controller not only offered an integral solution for position servo system in motion simulator, but also benefited to illustrate how to combine MAS methodology with RCP technology in complex control system design. By applying MAS methodology, motion simulator's control system was partitioned into cooperated controller agents with clear hierarchy. Digital controller in this paper was implemented as an agent controller corresponding to the role on an actuator's position control. According to the division of controller's agent task, hardware and software platforms were modularized. Furthermore, the software platform was coded using Matlab/Simulink and RTW based on RCP technology, which is distinguished with classic MAS methodology. By integrating RCP technology with MAS methodology, a seamless and efficient route for control system design was provided from system requirement to practical digital controller and the performance of this controller was also investigated.

In this paper, an improved feed-forward inverse control scheme is proposed for transient waveform replication (TWR) on an electro-hydraulic shaking table (EHST). TWR is to determine whether a test article can remain operational and retain its structural integrity when subjected to a specific shock and vibration environment. Feed-forward inverse transfer function compensation is a useful technique to improve the tracking accuracy of the TWR on the EHST system due to their inherent hydraulic dynamics. Whenever a feed-forward inverse transfer function is employed, it is critical to design the identification accuracy of the inverse transfer function. A combined control strategy, which combines a feed-forward inverse transfer function compensation approach with a simple internal model control (IMC) and a real-time feedback controller, is proposed to minimize the effect of the system uncertainty and modeling error, and further to improve the tracking accuracy of the TWR. Thus, the proposed control strategy combines the merits of feed-forward inverse transfer function compensation and IMC. The procedure of the proposed control strategy is programmed in MATLAB/Simulink, and then is compiled to a real-time PC with Microsoft Visual Studio.NET for implementation. Simulation and experimental results demonstrated the viability of the proposed combined control strategy.

According to the basic motion requirements of quadruped robots, the mechanism of quadruped robot with 12 degrees of freedom is designed, and the dynamic model of single leg and the description equation of foot position are established. In order to solve the problem of the joint torque optimization of quadruped robots in swing phase, a method of generating the foot trajectory based on dynamics is proposed. Computer simulation results show that the proposed method can reduce the torque output of quadruped robot joints when the quadruped robots are in swing phase and prove the reliability of the proposed method for quadruped robot in the foot trajectory generation. Finally, because the leg structure of quadruped robot has the general characteristics of typical series linkage mechanism, it can also be extended to other series mechanisms with multiple connecting rods.

Idiopathic scoliosis (IS) is a complex three-dimensional (3D) deformity. The non-operative treatments for IS have been developed for a long time. According to current studies, hard braces are more effective than soft braces for the treatment of scoliosis. Though current braces are proved to be effective for the treatment of IS, there are several shortcomings needed to be overcome: (i) Braces cannot realize precise control over a specific vertebra. (ii) Braces affect cardiopulmonary efficiency (braces limit maximal exercise performance). (iii) The brace is not modulated based on user’s needs. (iv) Braces, including motions during eating, tying shoes, sitting, and standing. (v) Braces apply forces on skin, which causes pain, skin breakdown, and abnormal deformation of bone. In order to solve these boring problems of the current braces, this paper proposed a new intelligent robotic spine brace based on the principle of human biomechanics, three point pressure treatment theory and parallel mechanism theory. This novel brace can offer 3D active dynamic adjustable corrective forces for the treatment of IS and some experiments are employed for verifying the effect of the proposed brace.

A novel dynamic brace for the treatment of idiopathic scoliosis based on parallel-actuated robotic system is proposed in this paper. The new brace can apply corrective forces on patients’ spine actively to correct the abnormal spine. However, the gravity of the dynamic system results in some adverse impacts, such as reducing comfort degree of patients, accuracy loss of rehabilitation force control, big error in direction and value of force. To overcome this problem, a new active force control strategy, proportional-derivative (PD) control with desired-gravity-compensation (DGC), is proposed to improve the effectiveness of scoliosis rehabilitation. Considering the electrically driven system and the environment contacting with the brace, the dynamic model of the active brace system is derived using Kane method. Based on the above mentioned, the force controller with DGC is designed for the brace system to compensate the impact of system gravity. The brace experiment system is built and various experiment tests are performed to verify the proposed control strategy. Experiment results demonstrate that the proposed control strategy, PD control with DGC, can distinctly reduce the influence of the brace system gravity and has more efficient control effectiveness compared with the classical PID controller.

A combined control strategy with an adaptive inverse control (AIC) and an inverse frequency response function (IFRF) equalization technique is proposed for the electrohydraulic shaking table (EST) system. The control purpose is to improve the accuracy of time waveform replication. In contrast to the iterative compensation through repetitive excitations control approach of industrial EST controllers, the proposed control strategy utilizes an IFRF of the EST system for extending the EST system frequency bandwidth and obtaining asymptotic reference tracking, and employs a variable tap-length filtered-x least-mean-squares algorithm to adaptively tune the time-domain drive signal and further improve the position and acceleration tracking performance of the EST system. Thus, the proposed combined control strategy is designed to combine the merits of IFRF and AIC. The procedures of the proposed control strategy are programmed in MATLAB/Simulink, and then compiled to a real-time PC with Microsoft Visual Studio.NET for implementation. The simulated and experimental results show that this control strategy achieves satisfactory position and acceleration waveform replication accuracy.

The dynamic model of the hydraulic control system of the shift clutch is established through the flow equation of the valve port, the flow continuity equation and the balance equation of the valve core force, the piston motion of clutch cylinder is divided into three stages. And simulate the dynamic curves of the hydraulic pressure of the hydraulic inlet of the hydraulic cylinder during different stages.

Keywords: Motion simulator; Dynamic model; Movement decomposition; Model simplification Abstract. Highly nonlinearity and strong dynamic coupling exist in 6-DOF motion simulator. Usually, in order to make the system has good dynamic and static quality, a good controller need to be designed according to the nature of the dynamic model. Therefore, the research about the simplified dynamic model used for real-time solution will be very meaningful. First, KANE method is used to build complete compact multi-rigid-body dynamic model. Second, rigid body and movement decomposition method are used to split dynamic model. On this basis, simplified strategy of the dynamic model of 6-DOF motion simulator based on dynamic contribution factor is proposed. Finally, the simulation verifies that the simplified dynamic model can be real-time calculated with high efficiency.

Based on extensive study on literatures of control of parallel manipulators and serial manipulators, control strategies such as computed torque control, PD+ control, PD with feedforward compensation, nonlinear adaptive control are classified into two categories: model-based control and performance-based control. Besides, as advanced control strategies, robust control and passivity-based control for the parallel manipulators are also introduced. Comparative study in view of computation burden and tracking performance are performed. It turned out that the physical structure properties of parallel manipulators’ dynamics are similar with that of serial ones, and this constitutes a common foundation for the two kinds of manipulators to develop together that control design of parallel manipulators can start with ever established control methods of serial manipulators.

The Space End Effector Capturing Hybrid Simulation System is proposed in the paper, the system can be used to simulate the Space End Effector Capturing a Target Spacecraft and test the Space End Effector on the ground. The force and torque of the Space End Effector and the Target Adapter are measured by two 6-DOF force sensors in the system, and the relative motion of the Space End Effector and the Target Adapter can be calculated by the built capturing dynamics model. Then the relative motion is implemented by a hydraulic driven Stewart platform. For the simulation system, the dynamics calculation method is presented to construct dynamics simulation external loop. The stability of the external loop is analyzed to obtain the stability condition. At last, the virtual prototype of Space End Effector Capturing Hybrid Simulation System is built in ADAMS/Simulink. On the basis of these analyses, the whole process of the Space End Effector capturing a Target Spacecraft is simulated successfully.

Sine swept vibration experiment using traditional PID control strategy represents poor accuracy. For this reason, this paper proposes the error compensation control strategy Based on multiple offline iteration. The proposed strategy applies the H1 estimator method to identify the system frequency response function (FRF) and then combines the identified FRF, Fast Fourier Transform (FFT) and inverse Fast Fourier Transform (IFFT) technique to correct the input sine swept signal to implement the sine swept test. The error of the expected output signal and the experiment output signal is calculated and corrected using FFT, IFFT and FRF to compensate the input signal. The updated input signal is used to implement the sine swept test again and so on, until the output signal meets the accuracy requirement. The procedure of the proposed control strategy is programmed using the software MATLAB/Simulink and then compiled to a real-time PC with Microsoft Visual Studio.NET for implementation. Simulation results, backed up by corresponding experimental ones, demonstrate that the proposed control strategy achieves satisfactory accuracy with offline iteration twice.

In this paper, a scheme for digital servo-controller of three-axis six-DOF shaking table based on DSP is put forward after analyzing the three states feedback control of the shaking table. TMS320C28335 is used as the processor for data processing unit to carry out the control variables. TMS320C2812 expanded with AD7665 and AD7846, is adopted to acquire analog and digital signals, and is also used as the generator of the driving signal for the servo control system.CY7C025(one dual-port static RAM) is adopted to accomplish the data sharing between the data processing unit and the data acquisition system. Simulated and test results show that the digital controller works well and the shaking table servo-system gains excellent stability and more wide system frequency bandwidth.