RT Mover
A four-wheel robot concept with a simple mechanism and high mobility for all-terrain usage. The robot has four drivable wheels and two leg-like axles. Each wheel is mounted on one side of the leg-like axles at the front and rear of the body. RT-Mover has four active wheels and only other five active shafts, therefor the robot can move on discontinuous rough terrain whilst keeping a sheet part of the robot horizontally. It can move like a wheeled robot and also walk over a step like a legged robot.
Chiba Institute of Technology
Specifications
| Length | 800 | mm |
| Width | 450 | mm |
| Height | 134 | mm |
| Wheel size | 100 | mm radius |
| 30 | mm width | |
| Weight | 21.5 | kg |
| Motor (DC Servo) | 23 | W (Steering: 2; Sheet’s pitch: 1) |
| 40 | W (Wheel: 4; Sheet’s roll: 2 (front and rear)) | |
| Gear ratio | 40 | (Sheet’s pitch: 1 (warm gear) |
| 100 | (Wheel: 4; Sheet’s roll: 2 (harmonic gear) | |
| 400 | (Steering: 2; (Harmonic gear: 100; Belt drive: 4) | |
| Sensor | Posture angle sensor | |
| Encoder and current sensor (each motor) | ||
| Power supply | 24 | V Battery |
Overview
The robot has four drivable wheels and two leg-like axles. Each wheel is mounted on one side of the leg-like axles at the front and rear of the body.
RT-Mover has four active wheels and only other five active shafts, therefor the robot can move on discontinuous rough terrain whilst keeping a sheet part of the robot horizontally. It can move like a wheeled robot and also walk over a step like a legged robot.
The robot has four contact points on the ground, the minimum number to maintain stability when it raises one leg with supporting its body with the other three legs. Each wheel is attached to the tip of a leg, because in many cases, there is not enough space available to set the leg and wheel separately on the body of the robot. When the robot moves on a slope, the user and the load are maintained in a horizontal position.
The robot uses the Ackermann steering mechanism for direction control. Each wheel is driven and controlled independently.
Control system
The RT-MOver is equipped with two SH4 boards, one for control-ling the robot and the other for processing the posture angle sensor data. An I/O board is connected to the SH4 board for controlling the robot, and all data are inputted or outputted through the I/O board. The two SH4 boards are linked by socket communication. The robot is controlled in real time using ART-Linux.
References
Describes the technology, related work, the mechanical design, steering, and the function of the legs. Describes its moving strategy for rough terrain, and the simulations. Goes into the system configurations, and experimental results.
The mechanical design concept for RT-Mover is discussed, and strategies for moving on rough terrain are proposed. The kinematics, stability, and control of the robot are also described in detail. The performance of the proposed locomotion is evaluated through simulations and experiments
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