Research on a Biped-wheel Wall-climbing Robot System

Global Perspectives on Artificial Intelligence (GPAI) Volume 3, 2015 doi: 10.14355/gpai.2015.03.001

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Research on a Biped-wheel Wall-climbing Robot System Liu Aihua *1, Wang Hongguang 1, Yang Guoyong 12, Jiang Yong 1 State Key Laboratory of Robotics,Shenyang Institute of Automation,Chinese Academy of Sciences, Shenyang 110016, China 1.

University of Chinese Academy of Sciences, Beijing 100049, China

2.

liuaihua@sia.cn; 2hgwang@sia.cn; 3gwyang@sia.cn; 4jiangyong@sia.cn

*1

Abstract This paper introduce a biped-wheeled wall-climbing robot system for terrorism investigation. This system includes the bipedwheel robot mechanics, PDA remote control module, and wireless video transmission module. The robot mechanical configuration and structural characteristics are introduced. The robot has three work modes: moving straight, turning in plane and traversing cross-wall. Experiments show that the robot has rapid moving speed, excellent manoeuvrability and strong ability of traversing cross-wall.

Keywords Investigation; Wall-climbing Robot; Biped-Wheel; DSP and CPLD Controller

Introduction For inspecting the dangerous environment such as anti-terrorist combat, the use of remote operated robots improves the combat effectiveness and protects the safety of the combatants. Small-scale robot design has become a hot research topic recently. Wall-climbing robot is one special robot type satisfying the needs of remote investigation. Researchers developed various types of wall-climbing robots in the past 20 years mainly in three categories: wheeled, footed and crawler. The authors of [1-2] mainly introduce the footed robots featuring structural diversity, movement flexibility and obstacle avoidance capability. But the footed robots have relatively slow speed. [3-4] discuss wheeled wall-climbing robots which have the advantageous high mobility, but only for relatively flat wall without obstacles.

The Wall-Climbing Robot System The investigation of wall-climbing robot consisted of a robot, a portable controller carried by the operator and relay equipment.Decided by the need of the investigation task, operator can control the robot through wireless remote control by PDA controller in a certain range. The wireless mini camera mounted on the robot can transmit the realtime image acquired to the operator and further station by the video module.

FIGURE 1 THE WALL-CLIMBING ROBOT

FIGURE 2 THE CONTROLLER AND RELAY EQUIPMENT

The robot consisted of its mechanism, control system, inner/outer sensors and mini camera, while the relay equipment includes the power and video relay system. The portable controller is designed based on PDA.The robot connects to the PDA by wireless communication. Two-way wireless data transmission between PDA and robot is achieved by serial port Bluetooth. PDA sends commands to the robot while receiving the state information from the robot which includes sensor data, joint data and robot state information.

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Mechanism Configuration of the Robot The robot is designed based on vacuum adsorption. Two sucker feet connected with a semi -cylinder respectively while two semi-cylindrical outer surfaces consists an outer gear pair. Two half-cylinder connected by rods at the center of its rotation by turning deputy.Shown in figure 3, the robot mechanism has four degrees of freedom: four rotary joints and a movement joint.Wherein, the rotary joints J2 and J3 are placed in horizontal direction.Motor 2 drives J2 to achieve the relative rolling of two half cylinders.Rotary joint J1 and J4 are vertically placed and driven by motor 1 and motor 3 respectively to achieve plane rotation respectively. Movement joint 5 is placed vertically and driven by motor 4 to achieve vacuum cup 2 elongations or contraction to help the robot to traverse cross-wall.

Cup 1 connects to half-cylinder 1 through rotary joint J1, while cup 2 connects to half-cylinder 2 by movement joint J5 and rotary joint J4. Two half-cylinders are connected by rods through rotary joint J2 and J3. Three of them compose the planetary gear train.

The robot can move straight, turning in plane and traversing cross-wall through relative rolling of two semicylinders and alternate adsorption and release of two vacuum cups. The robot mechanism is asymmetric. The size and weight of the robot is reduced by compositing movement and attitude adjustment, compacting structure and reducing the number of motor

Rotary joint J4 （Motor 4）

Rotary joint J1 （Motor 1）

Movement joint J5 （Motor5）

Rotary joint J2 （Motor 2）

Rotary joint J3

O1

Vacuum cup 1

O2

Vacuum cup 2

FIGURE 3 ROBOT INSTITUTION SKETCH

Robot Body Control System Wall-climbing robot control system consists of a robot body controller module,a PDA remote controller, a Bluetooth-based up/down PDA communication module and a power module.The body controller based on DSP and CPLD realizes motion planning and control according to the PDA and robot sensor information. PDA sends control commands and monitors robot’s state.Robot communicates with PDA through communication module based on Bluetooth. Power module is used to convert, monitor and manage power supply for the entire system.

Robot body controller module is the core part of the whole control system, which is designed by DSP and CPLD.According to the system design requirements, we choose EPM1270 chip from Altera's MAX II family.

EPM1270 has 1,270 logic elements (LE), 116available I / O pins and 8192 bits of user memory.CPLD is used for multiple motors logical control, which is PWM logical design for motor speed and direction control, and the circuit logical design to capture the motor quadrature encoder pulse.

As shown in figure 4, control system based on DSP and CPLD includes central processor, joint motor drive interface, communication interface, debug and download interface, pneumatic drive interface, sensor interface and power system.

1) Central processor: core part of the control system for the robot to complete real-time multi-task management.

2) Joint motor drive interface: generates 4 motor control PWM signals, which drive motors through power amplifier chip SN754410. capture motor encoder signals , read the current position of the motor 3) Communication interface: two-way wireless data transmission between controller and robot is achieved by serial port Bluetooth.

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4) Debug and download interface: standard JTAG debug interface to download configuration information and system programs.

5) Pneumatic drive interface: control the on/off of pump and switch value through general I/O port, the signal is amplified by 9014 and 2N4410 to drive the pump and switch, then control the adsorption and release of the vacuum cups.

6) Sensor interface: read sensor information on the robot, which includes the tactile sensor information from I/O port and pressure sensor information after A/D convert.

7) Power system: there is an 9V power system, then changed to 8V, 5V, 3.3V and 1.8V by a number of power regular chips External sensor information acquisition circuit

Pressure Sensor Tactile sensor Limit sensors

Motor 1

Serial communication interface circuits

DSP2812

CPLD

JTAG debug interface circuit

Joint motor control circuit

Motor 2 Motor 3 Motor 4

Vacuum cups control circuit

pump switch

pump switch

FIGURE 4 CONTROL SYSTEM

Locomotion Modes Biped-wheel wall-climbing robot has three movement patterns: movingstraight, turning in plane and traversing cross-wall.The followings are detail analysis of three movement patterns Moving Straight Robot can walk straight along the wall by relative scrolling of two semi-cylinders and alternate adsorption and release of two vacuum cups.Take initial state of vacuum cup 1 adsorbs on the plane as an example, so does when the cup2’s adsorption.

The moving straight steps are as follows: 1)Adsorb vacuum cup 1, release cup 2; 2)Motor 2 drives rotary joint J2 to achieve the rolling of semi-cylinder 2 relative to semi -cylinder 1; 3)Adsorb vacuum cup 2, release cup 1.

According to the principle of the planetary gear train, one step distance of the robot is the length between the centers of two semi-cylindrical, i.e., twice the radius of the semi -cylinder.

Turning in plane The robot has two vertical rotary joints in two half cylinders respectively. In single cup adsorption state, robot turns in plane the rotation of rotary joint J1 driven by motor 1 or J4 driven by motor 3.Take vacuum cup 1 adsorbs on the plane as an example, so does when the cup2’s adsorption.

1)Adsorb vacuum cup 1, release cup 2; 3

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2)Motor 1 drives joint J1. As a result, robot rotates a certain degree; 3)Adsorb vacuum cup 2, release cup 1.

Traversing Cross-Wall Robot repeats the action of rotary joint J2 and movement joint J5 to adjust the position and attitude of vacuum cups to achieve traversing cross-wall. Take traversing outer corner of the cross-wall when vacuum cup 1 adsorbs on the wall as an example to illustrate, other conditions may analogy: 1) Robot moves to the critical point of the cross-wall, then vacuum cup 1 adsorbs and release cup 2; 2) Motor 2 drives joint J2, two half cylinders roll relatively until cup 2 contact the target surface; 3) Motor 4 drives joint J5 to sxtend and contract cup 2; 4) Repeat steps 2 and 3, adjust the position and attitude of cup 2 until cup 2 adsorbs target surface.

Design of Remote Control System Remote control PC is X15v from DELL Axim series. Serial Bluetooth is used in control system to realize two-way wireless data transmission between the up/down computers, shown in figure 5: Human Interface

Operational interface

Working mechanism

Coding

Coding Bluetooth

Bluetooth Decoding

Decoding

Bluetooth underlying control

Robot Motion Control based on DSP And CPLD

Bluetooth underlying control

PDA

Robot

FIGURE 5 FIGURE 5 BLUETOOTH COMMUNICATION

Coding portion of the PDA converts selected operation information to six bit signal, then transmits the signal to processing module of the robot through underlying Bluetooth control signal.The signal processing module decodes the received signal, then sends it to the processor and converts it to corresponding action sequence.Thus, the remote control of reconnaissance wall-climbing robot is realized. DSPgets the working status of components by the sensors information and implementation of the instruction.Then, the information is encoded by certain rules and sent to PDA through serial Bluetooth module. After decoding, the information is shown on the PDA.In this way, we realize data bi-directional communication between the robot and PDA. A menu-driven human-computer interaction platform is designed in the environment of PDA.Man-machine interface is divided into two parts: the upper displays status information of the robot and operating steps; the underlying is operating control section.Status information is displayed in real time which is the running and working conditions of each component.The underlying control system is hierarchical menu to set the auto/manual, turn left/right, forward/backward, across the barrier and the control parameters(distance and angle).

Experiments According to the system design, processing, installation and commissioning, we developed a biped-wheel wallclimbing robot system.We tested the robot to verify the effectiveness of the mechanism and the design of control system, when moving straight, turning in plane and traversing cross-wall. Figure 6 is straight walking experiment.

Figure 7 is a turning in plane experiment. Figure 8 is an inner corner cross-wall traversing experiment. Figure 9 is an outer corner cross-wall traversing experiment.

According to the results, the robot system specifications are shown in Table 1.

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FIGURE 6 MOVING STRAIGHT PERFORMANCE TEST

FIGURE 7 TURNING IN PLANE PERFORMANCE TEST

FIGURE 8 INNER CORNER CROSS-WALL TRAVERSING

FIGURE 9 OUTER CORNER CROSS-WALL TRAVERSING

TABLE 1 ROBOT SPECIFICATIONS

Specification Robot Dimension (mm) Weight (kg) Voltage (V) Degrees of freedom Adsorption Average speed (m/min) Remote distance (m) Image transmission distance (m) Locomotion modes Ability to adapt to the wall

Test result 280*144*145 2 12 4 Vacuum 1.4 ≤50 ≤100 Walking straight, turning in plane and traversing cross-wall Smooth surface of metal, glass, etc.

Conclusions This paper introduces a new biped-wheel climbing robot system, including the body mechanical design, the DSP/CPLD control system, PDA Bluetooth wireless controllers and wireless video transmission module. This robot effectively combines the advantages of fast moving wheeled robots and footed robots with great obstacle cross ability. This proposed robot can move straight, make turn smoothly, and traverse the cross-wall surfaces. The experiments show that the design goal is achieved and the remote inspection tasks can be fulfilled by special robot system design.

ACKNOWLEDGMENT

This research work is conducted under the support of the National Natural Science Foundation of China under Grant 61179049.The authors acknowledge the support of Wang Hongguang, who is upervisor in Shenyang Institute of Automation, Chinese Academy of Sciences,The authors also would like to thank Jiang Yong，for their kindly and great helps to this paper.

REFERENCES

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Global Perspectives on Artificial Intelligence (GPAI) Volume 3, 2015

Zhang Pei-Feng. Research on mechanism and control methods of a miniature climbing robot[D]. Shenyang: Shenyang Institute of Automation, Chinese Academy of Sciences, 2006.

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Liu Aihua is a research assistant and holds master's degree. Her main research interests include special robotic mechanism and robot control.

Wang Hongguang is a professor and Ph.D. supervisor in Shenyang Institute of Automation, Chinese Academy of Sciences. His main research interests include robotic mechanism, advanced robots and mechatronics Yang Guoyong is working with his Ph.D in Shenyang Institute of Automation, Chinese Academy of Science. His main research interests include robotic mechanism, robotic kinematics and dynamics and air-bearing simulator Jiang Yong is a associate professor and Ph.D . His main research interests include robot control, intelligent control theory and method, embedded control system, special robotic system and application.He has published more than 20 papers.

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