1. Design of Motion Control System for Frog-inspired Bionic Hopping Robot
Qimin Zhang
Technology and Engineering Center for Space Utilization
Chinese Academy of Sciences
2017.5

2. Design of Motion Control System for Frog-inspired Bionic Hopping Robot
Introduction
Mechanical Model and Hopping Motion Strategy
Motion Control System
Hopping Experiment
Conclusion

3. Introduction
Hopping robot is a kind of robot which moves by jumping or bouncing gait. Bionic hopping robot is a typical research topic.
Certain animals with outstanding jumping capabilities, such as kangaroos, frogs and rabbits, are good references for designing jumping robot systems.
Cheetah Robot
Bionic Kangaroo

4. (complex and rugged terrain)
Introduction
Advantages of Hopping Robot
Adapting to harsh conditions and unstructured environment
Efficient movement pattern
Autonomous movement capability
Applications of Hopping Robot
planetary surface exploration
archaeological exploration
military reconnaissance
Moonscape
(complex and rugged terrain) 

5. Schematic Diagram of Half Side of Hopping Robot
Mechanical Model
Frog
Schematic Diagram of Half Side of Hopping Robot
A frog-inspired bionic hopping robot driven by elastic mechanical legs.

6. Hopping Motion Strategy
It is necessary to satisfy the constraint condition of the center of mass of hip in coordinate in takeoff phase:
a. means initial position, means the position at ;
b. means the velocity at .
According to the above constraint conditions, the expression of the vertical direction of the rising center of mass is:
Coordinate of the Robot
(1)

7. Hopping Motion Strategy
The mathematical expression of the above constraint equation:
Figure out （i=1,2,3,4）by the constraint conditions, then vertical displacement expression of center of mass of hip in takeoff phase:
(2)
(3)

8. Hopping Motion Strategy
Landing phase:
a. becomes in the landing phase;
b becomes 0 in the landing phase;
Then the constraint equation is:
Figure out （i=1,2,3,4）by the constraint conditions, then vertical displacement expression of center of mass of hip in takeoff phase:
(2)
(3)

9. Motion Control System
In order to improve the practicability of the robot, the semi autonomous control mode is adopted.
The communication between host computer and controller adopts Serial Communication Interface ( SCI ).
In order to improve the practicability of the robot, the semi autonomous control mode is adopted:
mission instructions issued by the operator at the control terminal
the robot actualizes its attitude adjustment and hopping independently
the working state information is fed back to the control system in real time.
Structure of Motion Control System

10. Hardware structure of motion control system
The motion control system of hopping robot is composed of host computer PC and embedded main controller(DSP-TMS320LF2407).
Hardware structure of the robot control system

11. Software structure of motion control system
Hardware structure of the robot control system

12. Main controller and divers
One TMS controls two LMD, which means 5 steering gears and 2 direct-current motors.
Structure of the main controller and divers

13. Main controller and divers
Embedded Controller Main Program Flow Diagram

14. Hopping Experiment
a） Horizontal Position of Mass Center b） Vertical Position of Mass Center
Displacement of Mass Center
The length is 260mm, the width is 96mm, the height is 140mm and the weight is about 0.7kg. The horizontal jump distance is about 845mm, and the maximum vertical jump height is 435mm in the hopping experiments.

15. Motion Control System
A slight vertical fluctuation exist in the landing phase
A buffer mechanism is added to the forelimb of the robot to have a more stable landing.
Two hind limbs of the robot can not be fully synchronized
The synchronization is improved by controlling the lag time of the hind limbs and adjusting the counterweight.

16. Conclusion
This paper proposes to design a hopping robot by imitating the movement of a frog. The frog-inspired bionic hopping robot has a strong capability of obstacle avoidance and high mobility.
The hardware structure and software system presented in this paper are universal, which are easy to transplant to the next-stage hopping robot or other bionic robots.
Motion mechanism
Motion control system
Experimental research on hopping motion of robot

17. Thank you!
Qimin Zhang
Technology and Engineering Center for Space Utilization
Chinese Academy of Sciences
2017.5