The dual-active-bridge (DAB) converter is applied for power transmission and voltage conversion in dc power grid. To improve the quality of input current, an input LC filter is cascaded to DAB converter. However, due to the interaction between LC filter and DAB converter, substantial oscillation and instability occur, leading to the excessive electromagnetic interference, large voltage ripple, and power loss and even operation failure. To solve this issue, an active damping strategy is proposed in this article to reshape the small-signal input impedance by parallel virtual impedance. The input voltage is regarded as a control objective, as well as the output voltage, therefore, a triple-closed-loop control structure is established. Besides, all dynamics of controllers are considered for the input impedance modeling of DAB converter. Moreover, compared with traditional methods, an active damping method for cascaded DAB converter with LC filter is adopted to design the virtual impedance and controller, suppressing resonance of LC filter and achieve a larger bandwidth. Therefore, a more stable and rapid dynamics cascaded system composed of DAB converter and LC filter are achieved. Finally, a prototype is set up and the effectiveness and superiority of proposed strategy are verified by experiments.

According to the characteristics of human gait and the requirements of power assistance, locomotive mechanisms and electrohydraulic servo driving are designed on a lower limb exoskeleton robot, in which the miniaturization and lightweight of driving system are realized. The kinematics of the robot is analyzed and verified via the typical movements of the exoskeleton. In this article, the simulation on the power of joints during level walking was analyzed in ADAMS 2016, which is a multibody simulation and motion analysis software. Motion ranges and driving strokes are then optimized. A proportional integral derivative (PID) control method with error estimation and pressure compensation is proposed to satisfy the requirements of joints power assistance and comply with the motion of human lower limb. The proposed method is implemented into the exoskeleton for assisted walking and is verified by experimental results. Finally, experiments show that the tracking accuracy and power-assisted performance of exoskeleton robot joints are improved.

This article discusses several new mechanisms that may be used in prostate cancer seed implant robotics. We have developed relatively simple but effective mathematical models of multi-needle puncture prostate using nonlinear spring–damper model; based on Automatic Dynamic Analysis of Mechanical Systems or dynamics module, displacement simulation for prostate is performed, and simulation results indicate that the multi-needle puncture mechanism could reduce prostate displacement in the y- or z-direction. Then aiming at the limitation of human body structure space and seed implant needle insertion path, a revolute-revolute-translational-type prostate seed implantation robot with three-dimensional transrectal ultrasound navigation is designed. It is noteworthy that drive torque fluctuation is caused by the center of gravity change of revolute-revolute tandem cantilever structure; an elastic balance mechanism is designed to realize the complete balance of cantilever weight. Based on Automatic Dynamic Analysis of Mechanical Systems or dynamics module, static drive torque simulation of 2-revolute tandem cantilever structure is performed. Finally, we manufacture the robot prototype and make verification experiment to the cantilever balancing device, and the experiment results provide evidence that elastic balance mechanism can realize the complete balance of cantilever weight, improve the fluctuation in the amplitude value of driving torque, and increase its operation stationary of seed implantation robot system.

This article focuses on the topic of the structural design of surgical radioactive surgery robot for prostate cancer. To improve the weight-to-payload ratio of surgery robot end-effector, the energy consumption and stability of robot joint drive and reducing the displacement and deformation of needle insertion in soft tissue. This article discusses the new static torque balancing method and multi-needle insertion soft tissue stabilization mechanisms that may be used in previously articulated seed implantation robots. Compared with the existing balancing system schemes, we adopt the idea of mutual conversion of gravitational potential energy and elastic potential energy and establish a static balancing model. With preloaded displacement parameter of the spring α, the variable gravity torque balance of robot arm can be achieved. Torque and equivalent gravity balancing distribution with the spring balance system and the quantitative evaluation experiment were performed, and experiment results provide evidence that these spring balance devices can basically compensate the gravity torque of the robot arm. In addition, we used nonlinear spring–damper model to establish multi-needles insertion soft tissue force model. Then, a variable multi-needle insertion soft tissue stabilization device is designed with six working modes. The innovative design of this device is the use of the first four needles that are introduced simultaneously on either side of the midline. Initially completed displacement simulation of different numbers of needle insertion prostate tissue, experiment results indicate that multi-needle puncture mechanism could reduce prostate displacement in the y- or z-direction. By this method, the prostate may be fixed, thus this mechanism maybe reduces rotation of the prostate and enabling subsequent needles to be inserted accurately.

This article focuses on the structural design of a surgical robot for radioactive prostate seed implantation and the position detection algorithm for the puncture needle. A seed implantation robot with the ability to pierce with force and receive image feedback is created to increase the positioning precision and puncture stability of the robot as well as to determine the real-time position of the puncture needle. Compared with existing puncture schemes, we use a statistical model approach for classification and a deep learning-based target detection algorithm. Since different human tissues have different structural properties, we conducted quantitative puncture experiments, and the experimental results demonstrated that this puncture scheme can effectively discriminate the punctured tissue and position the puncture needle tip, significantly improving the success rate of surgical radioactive seed implantation procedures.