Force Control Compensation Method with Variable Load Stiffness and Damping of the Hydraulic Drive Unit Force Control System

Each joint of hydraulic drive quadruped robot is driven by the hydraulic drive unit（HDU）, and the contacting between the robot foot end and the ground is complex and variable, which increases the difficulty of force control inevitably. In the recent years, although many scholars researched some control methods such as disturbance rejection control, parameter self-adaptive control, impedance control and so on, to improve the force control performance of HDU, the robustness of the force control still needs improving. Therefore, how to simulate the complex and variable load characteristics of the environment structure and how to ensure HDU having excellent force control performance with the complex and variable load characteristics are key issues to be solved in this paper. The force control system mathematic model of HDU is established by the mechanism modeling method, and the theoretical models of a novel force control compensation method and a load characteristics simulation method under different environment structures are derived, considering the dynamic characteristics of the load stiffness and the load damping under different environment structures. Then, simulation effects of the variable load stiffness and load damping under the step and sinusoidal load force are analyzed experimentally on the HDU force control performance test platform, which provides the foundation for the force control compensation experiment research. In addition, the optimized PID control parameters are designed to make the HDU have better force control performance with suitable load stiffness and load damping, under which the force control compensation method is introduced, and the robustness of the force control system with several constant load characteristics and the variable load characteristics respectively are comparatively analyzed by experiment. The research results indicate that if the load characteristics are known, the force control compensation method presented in this paper has positive compensation effects on the load characteristics variation, i.e., this method decreases the effects of the load characteristics variation on the force control performance and enhances the force control system robustness with the constant PID parameters, thereby, the online PID parameters tuning control method which is complex needs not be adopted. All the above research provides theoretical and experimental foundation for the force control method of the quadruped robot joints with high robustness.

Study on the Servo Drive of PM-LSM to Be Used in Parallel Synchronous Drive

Recently, linear motors can have high speed control, high acceleration-deceleration. So linear motors are widely used in industrial applications such as precision machine tools. In our laboratory focusing on transport system, we propose parallel synchronous drive of used the PM-LSM （permanent magnet linear synchronous motor）. It can pass luggage without having to stop the working. When you establish ＂parallel synchronous drive＂, a motor follows the other motor. In our laboratory, one of the motors is called ＂master motor＂ and the other motor called ＂slave motor＂. The master motor＇s speed and position pass slave motor then establish parallel synchronous drive. Therefore, slave motor requires high-responsive and precision that follows the master motor. This paper focuses on the control of the slave motor.

Systematic improvement in Tong's B-type water drive method

Tong's B-type water drive method was proposed as early as the 1970s and has been widely applied in the dynamic prediction and effective evaluation of oilfield development.Through extensive applications and studies,many researchers found that the statistical constants in the formula of the Tong's B-type water drive method(also referred to as the Tong's B-type formula)are not applicable to multiple types of reservoirs,especially low-permeability ones,due to the limited range of reservoir types when the formula was conceived.Moreover,they put forward suggestions to improve the Tong's B-type formula,most of which focused on the research and calculation of the first constant in the formula.For oilfields in the development stages of high or ultra-high water cuts,it is widely accepted that different types of reservoirs have different limit water cuts.This understanding naturally makes it necessary to further modify the Tong's B-type formula.It is practically significant to establish the water drive formula and cross plot considering that the two constants in the formula vary with reservoir type.By analyzing the derivation process and conditions of the Tong's B-type formula,this study points out two key problems,i.e.,the two constants 7.5 and 1.69 in the formula are not applicable to all types of reservoir.Given this,this study establishes a function between key reservoir parameters and the first constant and another function between key reservoir parameters and recovery efficiency.Based on the established two functions and considering that different types of oil reservoir have different limit water cuts,this study develops an improved Tong's B-type formula and prepares the corresponding improved cross plot.The results of this study will improve the applicability and accuracy of Tong's B-type water drive method in predicting the trend of water cut increasing for different types of oil reservoirs.

NUMERICAL SIMULATION OF STRESS-STRAIN DISTRIBUTIONS FOR WELD METAL SOLIDIFICATION CRACKING IN STAINLESS STEEL

This paper analyzed the characteristics of welding solidification crack of stainless steels,and clearly re- vealed the the of the deformation in the molten - the pool and the solidification shrinkage on the stress - strain fields in the trail of molten - weld pool.Moreover, rheologic properties of the alloys in solid - liquid zone were also obtained by measuring the hading and unloading deform curves of the steels.As a result, a numerical model for simulation of stress - strain distributions of welding solidifi- cation crack was developed. On the basis of the model,the thesis simulated the driving force of solidifi- cation crack of stainless steels, that is, stress - strain fields in the trail of molten-weld pool with fi- nite element method.

Attractive target wave patterns in complex networks consisting of excitable nodes

This review describes the investigations of oscillatory complex networks consisting of excitable nodes, focusing on the target wave patterns or say the target wave attractors. A method of dominant phase advanced driving （DPAD） is introduced to reveal the dynamic structures in the networks supporting osciUations, such as the oscillation sources and the main excitation propagation paths from the sources to the whole networks. The target center nodes and their drivers are regarded as the key nodes which can completely determine the corresponding target wave patterns. Therefore, the center （say node A） and its driver （say node B） of a target wave can be used as a label, （A, B）, of the given target pattern. The label can give a clue to conveniently retrieve, suppress, and control the target waves. Statistical investigations, both theoretically from the label analysis and numerically from direct simulations of network dynamics, show that there exist huge numbers of target wave attractors in excitable complex networks if the system size is large, and all these attractors can be labeled and easily controlled based on the information given by the labels. The possible applications of the physical ideas and the mathematical methods about multiplicity and labelability of attractors to memory problems of neural networks are briefly discussed.

NUMERICAL SIMULATION FOR THE SIMPLE SHEAR TEST IN AMORPHOUS GLASSY POLYMERS

In this paper , a driving stress finite element method ofelastic-plastic large deformation based on implicit time integratingalgorithm and an eight-chain molecular network model is used for thenumerical simulation of the simple shear test ofpolycarbonate(PC)materials. The simulated results are compared withexperimental ones. The strain localiztaion propagation for the shearband deforma- tion for simple shear deformation is investigatednumerically. The effects of microstructure parameters in the model onstrain softening and orientation hardening of the PC are discussed indetail.

The Practice Research of Task Driving Method in Basic Teaching of Information Technology

Purpose： It is used for judging the advantages and disadvantages of information technology foundation course teaching in health vocational colleges. Method： In teaching, it takes the two classes of 2012 grade nursing major as the experiment object. The comparison class adopts traditonal and speaking-practice combination teaching method and the experiment class adopts task-driving teaching method. When the semester finishes, it conducts testing andd questionnaire survey, collecting the relevant data, analyzing the changes of students in the aspects of performance, learning interest and attitude, autonomous learning consciousness and ability after experiment class adopting new teaching methods. Result： The exam performance of experiment class is obviously higher than the comparison class, and the experiment class has an obvious improvement in the aspects of learning interest, autonomous learning consciousness and ability, and the difference has statistical significance. Conclusion： The task driving teaching method is suitable for the status of information foundation teaching in health vocational colleges, which improves students＇ performance significantly and is good for students＇ learning interest and enthusiasm, obtaining good classroom effect. Also, it makes students＇ autonomous learning consciousness and ability improve greatly.

Hydrodynamics of high-speed robots driven by the combustion-enabled transient driving method

Underwater vehicles play important roles in underwater observation, ocean resource exploration, and sample collection.Soft robots are a unique type of underwater vehicles due to their good environmental adaptability and motion flexibility, although they are weak in terms of actuation and response ability. The transient driving method(TDM) was developed to resolve these shortcomings. However, the interaction between the robots’ swift motions and flow fields has not yet been fully studied. In this study, a computational fluid dynamic model is developed to simulate the fluid fields disturbed by transient high-speed motions generated by the robots. Focusing on the dependence of robot dynamics on thrust force and eccentricity, typical structures of both flow and turbulence fields around the robots are obtained to quantitatively analyze robot kinematic performance, velocity distribution, vortex systems, surface pressure, and turbulence. The results demonstrate the high-speed regions at the robots’ heads and tails and the vortex systems due to sudden expansion, indicating a negative relationship between the maximum fluid velocity and eccentricity. The reported results provide useful information for studying the environmental interaction abilities of robots during operating acceleration and steering tasks.

Activity enhancement of acetate precursor prepared on MnO_(x)-CeO_(2) catalyst for low-temperature NH_(3)-SCR: Effect of gaseous acetone addition

MnO_(x)-CeO_(2) catalysts are developed by hydrolysis driving redox method using acetate precursor(3 Mn1 Ce-Ac) and nitrate precursor(3 Mn1 Ce-N) for the selective catalytic reduction(SCR) of NO_(x) by NH_(3).A counterpart sample(Cop-3 Mn1 Ce) was prepared by the NH_(3)·H_(2) O co-precipitation method for comparison purpose.Combining the results of physicochemical properties characterization and performance test,we find that the 3 Mn1 Ce-Ac catalyst with some nanorod structures is highly active for the deNOx process.The SCR activity of the 3 Mn1 Ce-Ac catalyst is more admirable than the 3 Mn1 Ce-N and the Cop-3 Mn1 Ce catalysts due to plentiful Lewis acid sites,excellent low-temperature reducibility,and superior surface area resulted from O_(2) generation during the pre paration procedure.The 3 Mn1 Ce-Ac still exhibits the greatest performance for the deNO_(x )process when gaseous acetone is in the SCR feed gas.The NOx conversion and N2 selectivity over the 3 Mn1 Ce-Ac are both improved by gaseous acetone above150℃ due to the inhibition of SCR undesired side reactions(NSCR & C-O reactions) and "slow-SCR" process.

Underwater minirobots actuated by hybrid driving method

Underwater minirobots have attracted significant interest due to their value in complex application scenarios.Typical underwater minirobots are driven mainly by a soft or rigid actuator.However,soft actuation is currently facing challenges,including inadequate motional control accuracy and the lack of a continuous and steady driving force,while conventional rigid actuation has limited actuation efficiency,environmental adaptability,and motional flexibility,which severely limits the accomplishment of complicated underwater tasks.In this study,we developed underwater minirobots actuated by a hybrid driving method(HDM)that combines combustion-based actuators and propeller thrusters to achieve accurate,fast,and flexible underwater locomotion performance.Underwater experiments were conducted to investigate the kinematic performance of the minirobots with respect to the motion modes of rising,drifting,and hovering.Numerical models were used to investigate the kinematic characteristics of the minirobots,and theoretical models developed to unveil the mechanical principle that governs the driving process.Satisfactory agreement was obtained from comarisons of the experimental,numerical,and theoretical results.Finally,the HDM was compared with selected hybrid driving technologies in terms of acceleration and response time.The comparison showed that the minirobots based on HDM were generally superior in transient actuation ability and reliability.