Chuangqiang Guo

A Novel Absolute Magnetic Rotary Sensor

To measure the angular position of motors, robot joints, etc., an absolute magnetic rotary position sensor is developed, which possesses small-size, light, robust, and easy-to-integrate properties. The sensor consists of two inductors, i.e., a code disc and a signal processing part. Both of the two inductors are embedded with a big planar spiral copper coil and four smaller copper coils by employing microelectromechanical system (MEMS) technology, and there are two circles of regular copper sheets listing on the surface of the code disc. In addition, mathematical analyses of the inductor structure as well as the relationships of position and dimension among the coils and the copper sheet are addressed. Finite-element simulation results demonstrate that one group of the optimal sine and cosine signals can be generated by each inductor. Then, the absolute position measurement method is validated by a mathematical method. Finally, experiments are performed on the high-speed and the low-speed testing platforms to assess effectiveness and accuracy of the sensor.

Parameter identification and controller design for flexible joint of Chinese space manipulator

Manipulators with flexible joints are widely used as the space manipulators, whereas the elasticity of flexible joint leads to poor dynamic performance. To solve the influence of elasticity, the paper is to establish the model of flexible joint, identify the parameters, and design the controller. The off-line methods are applied to identify the current coefficient and the parameters of flexible joint model. The controller is designed based on the theory of state feedback and pole assignment. To make the calculation of controller gains easier, more precise and more intuitive, the nominal stiffness is introduced. The simulation results and the experimental results indicate that the proposed controller can improve the dynamic performance and reduce the vibration of the manipulator compared with the traditional PD controller.

Kalman smoothing with soft inequality constraints for space robot teleoperation

Space robot teleoperation system with haptic device has two operation modes: offline teleoperation mode and online teleoperation mode. High acceleration and jerk produced by the teleoperation system may degrade the performance of trajectory tracking and cause large residual vibration. In this article, human hand is treated as a kind of sensor, and two smoothers based on the standard Kalman smoother have been proposed to limit the acceleration and jerk in joint space in a certain range. On the one hand, the offline smoother for offline teleoperation mode makes use of a smoothing algorithm proposed in the literature, which is based on the interior point techniques. On the other hand, the online smoother for online teleoperation mode is proposed and named as reduced-Q method, which is a fixed-lag smoother with adjustable measurement noise. Experimental results have shown that the methods can constrain the acceleration and jerk of the trajectories in joint space within the specified range approximately and can improve the tracking accuracy without causing too many deformations. Thus, the psychology burden of operator will be alleviated.

Design of an upper-body humanoid robot platform

This paper presents a newly developed upper-body humanoid robot platform. The system has more than 52 degree of freedom (DOF), including two 7-DOF arms, two 15-DOF dexterous hands, a 3-DOF head, a 2-DOF waist and a 3-DOF mobile vehicle. To shorten development period and reduce cost, all the DOFs of the arms and the waist are designed with the modular joints. The two arms and two dexterous hands are identical. A control system with three hierarchical levels (including the teleoperation level, the central level and the joint control level) has been established to realize the control of the robot. Moreover, a high-speed serial communication bus (named as PPSECO) has been developed to complete communication between the controllers in the central level and in the joint level. At last, the box grasping experiment have completed successfully on the robotic platform, and the experimental results show that the robot has good operation performance.

Design of 6-DOF accelerometer and application in impedance control of manipulators with flexible joints

This paper is to introduce a 6-DOF acceleration sensor by utilizing multiple linear accelerometers, which possesses the advantages of small volume, high reliability and easy-to-integrate, etc. A cylindrical spatial geometrical configuration is proposed as the distribution basis of linear accelerometers, which avoids the accumulative errors arising from the integral operation. Moreover, error model of the sensor is deduced and calibrated for further error compensation. Static experiments illustrate that errors of the sensor are compensated effectively. In order to compensate the inertial force and attenuate the bounce of end-effector at the contact transition instant of impedance control, a Kalman filter is adopted to compensated the inertial force of end-effector, which fuses tip position, orientation, acceleration and force/torque. Experimental results indicate the effectiveness of the proposed acceleration sensor, and the inertial force of the end-effector can be compensated effectively in impedance control.

A vibration suppression method for flexible joints manipulator based on trajectory optimization

How to reduce the vibration deformation of robot manipulators with flexible joint is a significant problem. A new approach based on simplified system dynamic model and genetic algorithms (GA) is developed to find an optimized trajectory in joint space for a three degrees-of-freedom plane flexible joints manipulator, to reduce the residual vibration of the robot on the occasion of fast position control. The method makes the strain energy stored in the flexible joints minimized through planning the links and joint motors arrive at the destination positions simultaneously, so the residual vibration would be suppressed accordingly. And a genetic algorithm, whose objective function is to minimizing the maximum elastic deformation of the robot joints, was used to find the global optimized desired trajectory. And the computer simulation results show that the proposed method, comparing with the traditional trajectory planning method based on inverse kinematics calculation, reduces the trajectory tracing error and the residual vibration amplitude considerably.

Software-based resolver-to-digital conversion and online fault compensation

A simple and cost-effective software-based resolver to digital converter together with a permanent magnet synchronous motor control system were presented. The proposed method incorporates software generation of the resolver carrier and using anti-tangent calculation for synchronous demodulation of the resolver outputs signal in such a way that there is a substantial savings on hardware like the costly carrier oscillator and associated digital and analog circuits for amplitude demodulators. And the faults of amplitude imbalance and imperfect quadrature of resolver signal can also be detected and compensated by software online. Computer simulation results demonstrate the effectiveness and applicability of the proposed scheme.

Design of real-time and open control system for Chinese space manipulator joint based on RTX

Due to the real-time requirements of the manipulators control, the dedicated control systems are required, which has the disadvantages of the high cost, complexity and lack of flexibility. The control software cannot be modified according to the users expectation in the application of new algorithms or secondary development for the close framework. To overcome the above shortcomings, the paper is to construct an open architecture manipulator host control system based on the traditional Windows system by extending RTX. The host control system communicates with the manipulators by the high serial data bus. Most of the control algorithms of the manipulator run on the host control system, and the vector control of the motor is located in the joint. Experiment results indicate that the RTX system achieves the deterministic control of the manipulator with high real-time performance on the same computer, takes the advantage of rapid prototype development of software, open architecture, better compatibility and real-time performance, which improves the efficiency in the development of manipulator and the application of new control algorithms.

Reconfigurable fault-tolerant joint control system for space robot

To reduce mass and cubage, a joint for space robot is design with a double star windings permanent magnet synchronous machine (DS-PMSM), a double windings permanent magnet break, two resolvers with double windings, a torque sensor with double strains. Two complete sub-control systems have been constructed based on Field Programmable Gate Array (FPGA). An isolatable interface port is designed between the two FPGAs, based on which the reconfiguration of the resource between the two sub-systems can be achieved. So some non-coincidence faults in the two sub-control systems will not affect the joints function. Power supply and a control method are designed to tolerant the fault of single FPGA and ensure the incessantly work of joint. Experiment results have validated the fault tolerant ability of the designed joint control system.

Joint driver and control design for large torque, long arm space remote manipulator

This paper presents an overview of the structure and requirements of a ground engineering model for a space remote manipulator system, with long arm and large torque driver capacity. The system consists of a 6 DOFs robot arm composed of six identical modular joints, and a large-error tolerated end effector. A FPGA based joint controller hardware structure is built to form a distributed control scheme of the robot arm, while a fourth-order hybrid controller based on the joint torque feedback is adopted to reduce the influence of joint flexibility, brought by the harmonic drivers and torque sensor, on the control precision. A single-joint control experiment, designed to lift up a load at the tip of a link, about two meters in length, is used to test the ability of trajectory tracking in the gravity field.