翻译部分：
英文原文
Mobile platform of rocker-type coal mine rescue robot
LI Yunwang, GE Shirong, ZHU Hua, FANG Haifang, GAO Jinke
School of Mechanical and Electrical Engineering, China University of Mining & Technology, Xuzhou 221008, China
Abstract: After a coal mine disaster, especially a gas and coal dust explosion, the space-restricted and unstructured underground terrain and explosive gas require coal mine rescue robots with good obstacle surmounting performance and explosion-proof capability. For this type of environment, we designed a mobile platform for a rocker-type coal mine rescue robot with four independent drive wheels. The composi- tion and operational principles of the mobile platform are introduced, we discuss the flameproof design of the rocker assembly, as well as the operational principles and mechanical structure of the bevel gear differ- ential and the main parameters are provided. Motion simulation of the differential function and condition of the robot running on virtual, uneven terrain is carried out with ADAMS. The simulation results show that the differential device can maintain the main body of the robot at an average angle between two rockers. The robot model has good operating performance. Experiments on terrain adaptability and surmounting obstacle performance of the robot proto- type have been carried out. The results indicate that the prototype has good terrain adaptability and strong obstacle-surmounting performance.
Keywords: coal mine; rescue robot; rocker suspension; differential; explosion-proof design 1 Introduction
In the rescue mission of a gas and coal dust explosion, rescuers easily get poisoned in underground coalmines full of toxic gases, such as high-concentration CH4 and CO, if ventilation and protection are not up to snuff. Furthermore, secondary or multiple gas explosions may be caused by extremely unstable gases after such a disaster and may cause casualties among the rescuers[1]. Therefore, in order to perform rescue missions successfully, in good time and decrease casualties, it is necessary to develop coal mine rescue robots. They are then sent to enter the disaster area instead of rescuers and carry out tasks of environmental detection, searching for wounded miners and victims after the disaster has occurred.The primary task of the robots in rescue work is to enter the disaster area. It is difficult for robots to move into restricted spaces and unstructured underground terrain, so these mobile systems require good obstacle-surmounting performance and motion performance in this rugged environment[2]. The application of some sensors used for terrain identification are severely restricted by low visibility and surroundings full of explosive gas and dust; hence, a putative mobile system should, as much as possible, be independent from sensing and control systems[3].Studies of coal mine rescue robots are just beginning at home and abroad. Most robot prototypes are simple wheel type and track
robots. The mine explora- tion robot RATLER, developed by the Intelligent Systems and Robotics Center (ISRC) of Sandia National Laboratories, uses a wheel type mobile system[4]. The Carnegie Mellon University Robot Research Center developed an autonomous mine exploration robot, called “groundhog”[5]. Both the mine rescue robot V2 produced by the American Remote Company and the mine search and rescue robot CUMT-1 developed by China University of Mining and Technology, use a two-track fixed type moving system[6-7]. These four prototypes are severely limited in underground coal mines. Rocker type robots have demonstrated good performance on complex terrain.All three Mars rovers, i.e., Sojourner, Spirit and Opportunity used mobile systems with six independent drive wheels[8-9]. Rocker-Bogie, developed by the American JPL laboratory has landed successfully on Mars. The SRR robot from the JPL laboratory with four independent drive and steering wheels consists of a moving rocker assembly system, similar to the four wheel-drive SR2 developed by the Univer- sity of Oklahoma, USA[10]. Both tests and practical experience have shown that this type of system has good motion performance, can adapt passively to uneven terrain, possesses the ability of self adaptation and performs well in surmounting obstacles. Given the unstructured underground terrain environment and an atmosphere of explosive gases, we investigated a coal mine rescue robot with four independent drive wheels and an explosion-proof design, based on a rocker as sembly structure. We introduce the composition and opera- tional principles of this mobile system, discuss the design method of its rocker assembly and differential device and carried out motion simulation of the kinematic performance of the the robot with on ADAMS, a computer software package. In the end, we tested the terrain adaptability and performance of the prototype in surmounting obstacles.
2 Mobile platform[11-12]
Of As shown in Fig 1, the mobile platform of the rocker-type four-wheel coal mine rescue robot includes a main body, a gear-type differential device,two rocker suspensions and four wheels. The the shell of the differential device is attached to the interior of the the main body The two extended shafts of the differential device are supported by the axle seats in the of lat-to early plate of the main the body and connected to the rocker suspensions installed at both sides of the main the body. of The four wheels are separately connected to the of bevel gear, transmission at the the terminal of the four landing stretch our legs. at The four wheels are independently driven by a DC motor is installed inside the landing stretch our legs. of the rocker suspension flameproof design of the to stretch our legs. has been developed,which includes a flameproof motor cavity from and a flameproof connection cavity. Via a cable entry device, the power and control of the DCmotor cables are connected to the power and controller of the main the body.
2.1 Rocker suspension 2.1.1 Function
The primary role of the rocker suspension is to provide the mobile platform with a mobile system that can adapt to the unstructured underground terrain,such as rails, steps, ditches and deposit of rock and coal dumps because of the collapse of the tunnel roof after a disaster. By connecting the differential device intermediate between the two rocker suspensions, the four drive wheels can touch the uneven ground passively and the wheels can bear the average load of the robot so that it is able to cross soft terrain. The wheels can supply enough propulsion, which allows the robot to surmount
obstacles and pass through uneven terrain.
2.1.2Structure
As shown in Fig. 1, the rocker suspension is composed of a connecting block, landing legs and bevel gear transmissions. The angle between the landing legs on each side of the main body is carefully calibrated. The legs are connected to the connecting block and the terminals, which in turn are connected to the bevel gear transmissions. Fig. 2 illustrates the cal. The DC motor is in the leg and fixed to the connecting cylinder. The motor shaft connects to the bevel gear transmission and the wheel is also connected to the transmission. The upper section has a blind center hole through witch a connection is formed to the bottom section, via a connection cavity.Through the cable entry device of the upper section,the motor power and control cable from the main body of the robot are put into the connection cavity and connect to the wiring terminals which, in turn,connect to the guidance wires in the wire holder. Another end of the guidance wires connects to the motor in the bottom section.
A coal mine environment is full of explosive gases;hence, a rescue robot must be designed to be flame-proof. The DC motors, for driving each wheel, are installed in the landing legs of the rocker suspensions.At the present low-powered DC motors, available in the market, are of a standard design and not flame-proof, hence a flame proof structure for these motors must be designed. Given the structural features of the rocker suspension, it is very much necessary that a flame proof design for the landing legs be carried out.There are two important points to be considered in this flameproof design. First, a flameproof cavity is needed, in which the standard DC motor is installed. Given the flameproof design requirements, a group of flameproof joints should be formed between the motor shaft and the shaft hole. Generally, the motor shaft made by the manufacturer is too short to comply with the requirement of flameproof joints, so the motor shaft needs to be extended. Second, a flameproof connection cavity should be designed to lead the cable into the connection cavity through a flameproof cable entry device. DC motors, especially brush DC motors, may generate sparks in normal running and when the motor load is high, the working current may be more than 5 A, which exceeds the current limit in Appendix C2 of the National Standard GB3836.2-2000 of China. Therefore, the motor power and control- cable cannot be directly in the connection cavity.Given these requirements, the landing legs have been designed as flameproof units, as shown in Fig. 2.An elongated shaft sleeve has been assembled from the motor shaft, with the same inside radius as that ofthe motor shaft and this is how the motor shaft is extended. The front flange of the motor is fixed to the intermediate plate of the connecting cylinder. The motor shaft with the shaft sleeve passes through the center hole embedded with a brass bush and then connects to the input gear of the bevel gear transmission at the end of the bottom section of the landing leg. Therefore, flameproof joints are formed between the motor shaft and the shaft sleeve, as well as between the shaft sleeve and the brass bush. The terminal of the bottom section of the leg connects to the connecting cylinder and a flameproof joint is formed between the external cylindrical surface of the terminal and the inner cylinder surface of the connecting cylinder.
There is also a flameproof connection cavity in the upper section of the leg. In order to save space, the guidance wire is sealed together with the wire holder using a sealant. The seat of the guide wire is installed in the hole of the upper section of the
landing leg.Another flameproof joint is formed between the wire holder and the hole. The cavity of the upper section connects to the rabbet structure of the bottom section, with yet another flameproof joint. There is a flame-proof cable entry device at the end of the upper section of the landing leg. Hence, a flameproof connection cavity is formed in the upper section of the leg.Based on the structure described, the standard DC motor was installed in the flame proof cavity of the bottom section of the leg. The power and control cables of the motor connect to the flameproof connection cavity of its upper section through a wire holder.Moreover, the cable from the flame proof main body of the robot connects to the connection cavity via the flameproof cable entry device. Thus, the flameproof design of the landing leg of the rocker suspension section was completed. 2.2 Differential device[13-15]
2.2.1 Characteristics of the differential mechanism The differential Mechanism of a rocker-type robot is a motion transfer mechanism with two degrees of freedom, which can transform the two rotating inputs into a rotating output. The output is the linear mean values of the two inputs. If we let 1 and 2 be two angular velocity
inputs,the angular velocity output, ω1 and ω2，wo rotational angle inputs and ω be rotational angle output, we have:
???1??22 ，
???1??22
Two rotational input components connect to the left and the right rocker suspension of the robot and the output component connects to the main body of the robot. In this way, the swing angles of the left and right rocker suspensions are averaged by the differential mechanism and the mean value, transformed into the swing angle (pitching angle) of the main body, is the output. It is effective in decreasing the swing of the main body and thus reduces the terrain effect. Taking the main swing angle of the main body as input and the swing angles of the left and the right rocker suspension as outputs, the rotational input is decomposed into two different rotational outputs. If the output is the mean value of two inputs, it is helpful to allocate the average weight of the body to each wheel which can adjust its position passively alone in the terrain.Given the characteristics and operating requirements of differential mechanisms, a bevel gear type differential mechanism has been designed. We have analyzed the working principle of the bevel gear differential mechanism and present its detailed structural design.
2.2.2 Principle of the bevel gear differential mechanism
Fig. 3 shows the schematic diagram of the bevel gear differential mechanism. Two semi-axle bevel gears 1 and 2 mesh with the planetary bevel gear 3 orthogonally. Carrier H connects to planetary bevel gear 3 coaxially. Let the angular velocities of gears 1,2, 3 and carrier H be ω1、ω2、ω3 and ωH . Let the number of their teeth be Z1 , Z 2 and Z3 , where Z1, Z2 . Let the rotational angles of gear 1, 2 and carrier H be φ1、φ2、φH . If we let the relative H then we have:
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