Key Engineering Materials Vol. 621

Abstract: To develop the control system of multi-range hydro-mechanical continuously variable transmission (HMCVT), a model of a multi-range HMCVT is built using the principle of dynamics. According to the characteristic of power split, HMCVT is separated as axes set, variable displacement pump-motor system, clutch set. With wheel tractor as application instance, the whole model of vehicle power train is made, which includes the engine, HMCVT, running system and control system. Based on the theory of Finite State Machine, an automatic control method of speed change and range shift is present, which employs the throttle value, engine speed, range number and transmission ratio as the control parameters. The dynamic characteristic of automatic speed changing and ranges shifting is simulated. The result indicates that the model can correctly represent the dynamic characteristic of HMCVT, the engine can run at the optimal working point, the multi-range HMCVT can shift range steadily and change transmission ratio continuously when the load changes, the circularly shift range is avoided. The model can be used conveniently for the analysis of vehicle dynamic performance and the research of multi-range HMCVT control method.

Abstract: The research actuality and development of roller module replacement technology are talked over in this paper. Positioning scheme of one plane and two pins with the special rounded edge diamond pin that is suitable for the longer roller is discussed, which is meeting the parallelism tolerance requirement for the roller within the full length; thus reducing manufacturing tolerance requirement for the spacing between pin axes and reducing manufacturing difficulty. And on this basis, adaptable interface design of roller module rapid replacement system which is suitable for the longer roller has been completed. The invention patent on the roller module rapid replacement system has already been applied for, and the precise positioning of roller module can be realized.

Abstract: Torque motor is the electrical - mechanical converter of servo valve, is the bridge connecting electrical devices and hydraulic devices, is one of the key elements of electro-hydraulic servo valve. The main object of study of this paper is moving iron permanent magnet torque motor. The dynamic characteristics of torque motor are the key parameter to measure the overall performance. At present, the research of most of manufacturers emphasize on the test of integral valve servo valve. Torque motor is also designed to mimic the structure and size of foreign-based valve, lacking of system understanding for characteristics of servo valve. Early in the design, people cannot effectively control the overall performance of the torque motor products. There is large performance difference with a larger group of torque motor, producing serious waste. This paper describes the principle of dynamic characteristics test, establishes a test system of dynamic characteristics for torque motor, accurately obtain nature frequency and bandwidth of torque motor on the test bench which we have established before.

Abstract: Pressure type pneumatic measuring is the most wildly used method in overlap value testing, which depends strongly on the constant pressure of gas supplying. However,control of pressureisrarely done before.This paper presentsa design of a new overlap value measuring system with pressure control sub-system, mechanical platformand a program-controlled sub-system. A hybrid controller is developed combined with fuzzyself-adjusting PID and time-optimal control. The final version of this controller is a computationally efficient analytic scheme suitable for implementation in thereal-time closed-loop pressure digitalcontrol. At last, the system control software developed on LabVIEW is briefly introduced.

Abstract: To the world population aging serious problem, a research on assistant robot is more and more attention. Assistant Robot is a device that is similar to human exoskeleton. This device is worn by the operator, and keep consistent with the human walking and replace body to undertake cargo load. In this paper, based on the method of vector product, a 3-DOF assistant robot’s motion is analyzed. Jacobi matrix of robot motion is calculated. According to the experimental data from human walking, the assistant robot’s displacement and velocity vector and variation are simulated, and its variation are also analyzed. In theory, it proved that the velocity and displacement curves are continuous and smooth. Besides, it also provides references for control system design of the assistant robot.

Abstract: Flexible manufacturing cell (FMC) was the extension of the CNC machining center,which consisted of three portions , a CNC machining center , an industrial robot and unified by a the background computer programmable control. In order to guarantee the rationality and feasibility of the automatic operation loading and unloading workpieces , the simulation object was based on the KUKA robot of flexible manufacturing cell in this paper, which based on MATLAB/GUI and combinated of VRML language and information transmission method development between MATLAB and the simulation system of flexible manufacturing unit. According to the set up parameters and angles, the model was implemented. Through the control panel and the robot's real-time interactive simulation, 3d visualization window can be real-time display of the robot simulation, and validated the path planning. According to the simulation results of the model , it could provide reference to the actual movement of the KUKA robot trajectory planning, provided the better fully automated feasibility analysis of flexible manufacturing cell, and proved the improvement of flexible manufacturing unit operation scientifically and reasonably.

Abstract: Lunar rover is a special kind of wheeled mobile robot for deep space exploration mission. On the moon, the soft weathered layers, as well as different sizes of rocks and craters, are distributed disorderly and unsystematically. Facing such kinds of complex environments and terrains, the mobility and terrain trafficability performance of the lunar rover will be threatened to a certain extent. The SpaceDyn toolbox is adopted to build the six-wheeled lunar rover kinematics relation and to calculate the kinetic parameters. Then the lunar rover dynamics model can be achieved. The wheel-soil interaction model on soft terrain is established based on terramechanics theory. Finally, the coordinated driving controller for the six-wheeled lunar rover on complex soft terrain is designed according to the above model. Numerical calculation and computer simulations are performed to verify the performance of the designed controller on soft terrain. Results indicate that the lunar rover has a better coordination driving control ability when using the designed controller, which may provide a reference for motion control of other kinds of wheeled mobile robot.

Abstract: Error analysis and compensation of positioning is one of the basic problems for robot control. There are some limitations to study the error compensation either from the perspective of vision system or mechanism of the robot. Therefore, this paper studied the error compensation from both aspects with BP neural network model. Firstly, aiming at the depth values obtained by the vision system, a depth error database was established and based on BP neural network the depth error was effectively compensated within 5mm in MATLAB simulation. Secondly, aiming at the mechanism of a robot prototype the error compensation simulation based on BP neural network in MATLAB was carried out, and the simulation result showed that the error was within ±1mm after compensation. Thirdly, the correlative positioning error was defined and its error compensation simulation was carried out in MATLAB with the BP neural networks of the vision system and the mechanism; the simulation results showed that the correlative positioning error was approximately zero in this study. Finally, the error compensation of the robot mechanism based on the BP neural network was carried out on the robot prototype HNrobot2, and the experiment results showed that the positioning error was by 60% less, which was within 5mm.

Abstract: Target stereoscopic positioning is a significant sign of intelligent robot. The paper first described the research status of harvesting robot target stereoscopic positioning, discussed senor and stereoscopic positioning applications. Then, method and algorithm of rapid identification in target image were stated. In addition, version positioning, mechanism positioning, comprehensive positioning, associated positioning error, random positioning systematic error and application and existing problem of robot were introduced in this paper. Finally, harvesting robot positioning error compensation was proposed with the aiming at realizing robot precision positioning and expecting a great prospect of intelligent harvesting robot.

Abstract: Measuring robots’ real-time velocity correctly is important for locomotion control. Inertial Measurement Unit (IMU) is widely used for velocity measurement. Limited by the bias and random error, IMU alone often can’t meet the requirement. This paper makes use of Extended Kalman Filter (EKF) to fuse kinematics and IMU, and inhibits the drift successfully. We calibrate the bias and recognize the random errors of IMU. Then the forward kinematics of legs is established and the EKF algorithm for velocity estimation is designed based on IMU and kinematics. Finally, the presented algorithm is validated in simulation and on a quadruped robot based on hydraulic driver in trotting gait.