Deng Zongquan

Introducing HIT Spherical Robot: Dynamic Modeling and Analysis Based on Decoupled Subsystem

HIT spherical robot has been designed on the principle of carrying out the turning and driving motions independently in order to reduce dynamic complexity and realize real-time detection. After introducing the decoupling principle implemented in the working processing, we derive the dynamic equations about the two fundamental motions, i.e., rolling and turning. Hardware and software of the open-loop control system are introduced briefly and, in the following, experiments show that the robot can fulfill common exploration applying the proposed decoupling method.

Dynamic model building and simulation for mechanical main body of lunar lander

Focused on the dynamics problems of a lunar lander during landing process, the whole process was analysed in detail, and the linear elastic model of the moon soil was established by means of experiments-analogic method. Combining the way of elastic impact with the way of velocity replacement, the dynamics model of damping free vibration dynamics model with 3-degree of freedom(DOF) for lunar lander is obtained according to the vibration mechanics elementary theory. Based on Lagrange equations and the energy principle, the damping free vibration differential equations for the lunar lander with 3-DOF are derived and the equations are solved in simulation ways by means of ADAMS software. The conclusions obtained can be used for the design and manufacture of lunar lander.

Three-layer intelligence of planetary exploration wheeled mobile robots: Robint, virtint, and humint

The great success of the Sojourner rover in the Mars Pathfinder mission set off a global upsurge of planetary exploration with autonomous wheeled mobile robots (WMRs), or rovers. Planetary WMRs are among the most intelligent space systems that combine robotic intelligence (robint), virtual intelligence (virtint), and human intelligence (humint) synergetically. This article extends the architecture of the three-layer intelligence stemming from successful Mars rovers and related technologies in order to support the R&D of future tele-operated robotic systems. Double-layer human-machine interfaces are suggested to support the integration of humint from scientists and engineers through supervisory (Mars rovers) or three-dimensional (3D) predictive direct tele-operation (lunar rovers). The concept of multilevel autonomy to realize robint, in particular, the Coupled-Layer Architecture for Robotic Autonomy developed for Mars rovers, is introduced. The challenging issues of intelligent perception (proprioception and exteroception), navigation, and motion control of rovers are discussed, where the terrains’ mechanical properties and wheel-terrain interaction mechanics are considered to be key. Double-level virtual simulation architecture to realize virtint is proposed. Key technologies of virtint are summarized: virtual planetary terrain modeling, virtual intelligent rover, and wheel-terrain interaction mechanics. This generalized three-layer intelligence framework is also applicable to other systems that require human intervention, such as space robotic arms, robonauts, unmanned deep-sea vehicles, and rescue robots, particularly when there is considerable time delay.

Scheme Design of Extended Configuration for in-Pipe Robot Adapting Mechanism

The configuration design of in-pipe robot adapting mechanism has a significant impact on its motion performance. By analyzing the operation principle and structure composition of adapting mechanism, the four-bar linkage is chosen as basic unit to make topological combination, the two kinds of linkage combination including input of prismatic pair are presented, the configuration schemes that meet the given design constraints are also synthesized, and the application examples of specific mechanisms are given. Which provides a new method for configuration extended design of in-pipe robot adapting mechanism.

Development of Suspension Frame of New Eight-wheel Lunar Rover

To improve the evenness of distribution of the mass of a complete rover on the wheels can improve the consistency of the driving power of rover driving motors,and to improve the passive adaptability of suspension frame on loose terrain can improve the stability and obstacle crossing capability of the rover.Therefore,topological structure synthesis of the suspension frame of eight-wheel lunar rover with passive adaptability to terrain is carried out,and two structural types of usable eight-wheel suspension frames are determined.Then simulation analysis is carried out for the two types of suspension frames in respect of simultaneously crossing vertical obstacle with wheels on the two sides,adaptability to curved terrain,and smoothness and stability of movement of rover body.On the basis of the analysis results,appropriate structural type of the suspension frame of eight-wheel rover is determined, and the composition and working principle of the movement system of that are expounded.ADAMS software is used to optimize the parameters of structure of suspension frame,on this basis structural design of suspension frame and differential mechanism is carried out,and principle prototype is manufactured.Tests of performances of the prototype are carried out in respect of grade climbing and obstacle crossing.The test results indicate that the distribution of load on the wheels is even and the adaptability to terrain is strong.It can climb onto loose sandy land with a slope of 22°and cross an obstacle of 200 mm high.

The study of normal force model for the flow of lunar dust particles

Lunar dust can cause mechanical clogging and seal failures in lunar events, so it is essential to study the contact state of lunar dust particles which stuck in the mechanisms. The soft ball model based on Hertz theory is commonly used in particle contact problem. However, the assumptions of soft ball model are not applicable to lunar dust particles with irregular shapes and rough surfaces. To solve the problem, the power function model and exponential function model were proposed based on discrete element theory and nonlinear models in the rock and soil mechanics. The nonlinear relationship between normal force and displacement was obtained by static load compression test and the experimental data were imported into MATLAB to finish curve fitting. The experimental results show that the nonlinear stress-strain relationship of lunar dust particles can be most accurately described by the power function model. Meanwhile, the concept of equivalent elastic coefficient was introduced to simplify the simulating process. The lunar dust particles can be modeled as smooth spherical particles and the nonlinear stress-strain relationship can be described by equivalent elastic coefficient. With the new method, the theoretical model can be simplified and the simulation efficiency can be improved without affecting the model accuracy.

Design of the Low Gravity Simulation System for Planetary Rovers

A large scale gravity compensation system for planetary rovers is designed. The compensation system comprises a tension system and a position system: the tension system generates the constant tension of the string; the position system carries the tension system to follow the horizontal motion of the rover so as to keep the string vertical. To acquire rapidity and dynamic precision without resonating the position system, a macro-micro and open-closed loop design is brought forward: the coaxial macro and micro motors drive the winding drum to adjust the length of the cable; a constant-force mechanism is used to strain the string. The macro motor generates the majority of the tension and suppresses the low-frequency disturbance; the micro motor precisely adjusts the tension of the string to suppress intermediate-frequency disturbance; the constant-force mechanism suppresses high-frequency disturbance with its open loop performance. To precisely follow the rover over a large scale, a double position servo system is used: the girder-trolley system carries the two-dimensional platform; the girder-trolley system covers a large area but is sluggish and imprecise, and therefore is used to imprecisely follow the rover over a large area; the platform is precise and fast but covers a small area, and therefore is used to precisely follow the rover. The system covers a 30 m×30 m area. Experiments show that the position error does not exceed 0.01 m and the force compensation error does not exceed ±0.5% under normal working condition. When step interference emerges, the force compensation error does not exceed 1.5%.

Riding comfort analysis for two degrees model for mannedl lunarv vehicle

Two degrees of freedom of suspension vibration model was established for deployable manned lunar vehicle. Transfer characteristics and amplitude frequency characteristics of vibration response including body acceleration, suspension dynamic deflection and wheel relative dynamic load were obtained. Then lunar surface random excitation model in time domain was established according to the filtered white noise method. In order to analyze the affection of four parameters that is vehicle natural frequency, damping ratio, stiffness ratio and the mass ratio of two-degree system of manned lunar vehicle on mean square value of the vibration response, numerical integral approach was used to calculate. These provide theoretical basis for suspension design and riding comfort analysis for manned lunar vehicle.

Path Planning of Lunar Rover Group Based on Theory of Dynamic Programming and Multi-objective Optimization

A path planning of lunar rover group composed of one six-wheeled rocker-bogie master lunar rover and three spherical slave lunar rovers was presented for efficiency, safety and energy saving. The slave lunar rovers moved back and forth among nodes of every step for path survey. The objective value of every path to objects, which were energy and time consumption of the master rover and length of path, was calculated according to the concerted motion control based on the calculation on the pitch angle of rockers, kinematics analysis based on the velocity projection theorem and quasi-static analysis of the master lunar rover. Then dynamic programming and optimization of path was carried to the master lunar rover, using method of max relative membership degree of policy. Compared with the result of multi-attribute decision of path without the slave lunar rovers moving back and forth among nodes of every step, the dynamic programming and optimization of path saves energy.