With the deepening of ocean development, the tasks that underwater vehicles need to perform are more complex. Shared control provides a reliable scheme for robots to accomplish these tasks under teleoperation. At present, most of the underwater vehicles are equipped with a traditional mechanical manipulator, which is challenging to realize the application of shared control. So, we developed a highly humanoid underwater robot for shared control. The robot is equipped with two humanoid arms. It can be remotely controlled by the operator through the full ocean depth optical fiber, and can also realize simple task planning based on its control system. We have realized and improved the auxiliary function in the operation room, such as motion capture, data fusion, etc. We built detailed modeling and simulation analysis of the robot and used the sliding mode controller to achieve the stability control of the robot. Its reliability has been verified in the simulation and experiment. Finally, the robot completed the task autonomously in the offline state and showed a better control effect and stronger task completion ability under the shared control.
- shared control,
- Task analysis,
- Robot kinematics,
- Humanoid robots,
- Unmanned underwater vehicles,
- Mathematical model
At present, to deal with the complex underwater working tasks such as equipment maintenance, a series of underwater vehicles with the manipulator are developed . People can control the manipulator of the underwater vehicle remotely to complete simple works , and some can even realize the underwater interaction between the robot and the diver, such as Ocean One . However, most of these underwater vehicles use traditional controllers such as handle or gesture control , which obey the instructions of the operator .
Because the operator can only watch the video, it is challenging to handle delicate operation. In recent years, the emergence of shared control attempts to solve this problem and achieved good results in the remote control of the manipulator on the land . Although shared control can adapt to robots with different structures by joint mapping, the similarity between the structure of a manipulator and human arms still significantly affects its operation effect . At the same time, the robot using shared control also requires high autonomy to give operators enough support. In this paper, we developed a highly humanoid underwater robot and achieved its autonomy. Due to the anthropomorphic structure, the average mass distribution leads to the greater influence of arm movement on the balance of the body. We solved this problem through modeling and sliding mode control, and finally, used shared control to complete the scheduled tasks.
DEVELOPMENT OF THE ROBOT
- Hardware Description The humanoid underwater robot is designed to resemble a human shape, to make the movement space of hands, legs, and body closer to that of the operator. The overall size of the underwater robot is consistent with Asian adult males, shown in Fig. 1. The motion of the robot is controlled by the propulsion mechanism and the buoyancy adjustment mechanism in the cavity. The propulsion mechanism includes 8 screw propellers, which are driven by an integrated brushless motor. It is convenient for heat dissipation to encapsulate the driving chip at the bottom of the propeller outside the cavity.The buoyancy adjustment mechanism is composed of a stepping motor, screw rod, sealing chamber, and sliding piston. Buoyancy material is made of rigid polyurethane foam, mounted on the back and shoulders of the robot. It is used to balance the underwater weight, improve stability, and achieve the zero-buoyancy state of the robot.
There are two high-definition monocular cameras equipped on forward and downward of the head, which provide real-time underwater film. It can also provide the working state of arms and hands within the view range. The robot transmits all the information to the operation room through the high-speed full ocean depth optical fiber, so that the operator can see them on the interactive interface. The shoulder joints, elbow joints, and wrist joints of the robot’s arm are designed humanoid. Considering the task demand and the driving ability under zero-buoyancy state, we use the steering gear with 15kg/cm torque and 20W working power to drive the joint. The finger joints of the robot are respectively driven by shape memory alloy (SMA) wire, and the contraction of SMA wire is used to simulate the contraction of muscles, to realize the flexible grasp of the humanoid hands. Another paper will introduce the details of the humanoid Flexible Manipulator. The leg adopts a two-stage damping system, which can resist part of the external interference of the vertical plane
The pool test verifies the reliability of the software and hardware design of the humanoid underwater robot. The designed controller can make the robot keep the body stable in the process of using two arms. The overall deviation is less than 12 cm displacement, 25°Rolling angle, and 16° Yaw angle. In terms of motion control, it can complete 6- DOF motion and complete the task of accurately touching the 5 ∗ 15cm marks 2 meters away. Due to the high humanoid structure, it also shows good performance in the application of shared control, which can save 25% of the operation time. At the same time, the auxiliary motion capture system can collect the operator’s actions without any mark, which makes the operator more focused on completing the task. In the future, we will further optimize the software and hardware design of the robot, improve the control algorithm. At the end of 2020, underwater equipment maintenance tests will be conducted in the South China Sea.
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FULL Paper PDF file:Development and Control of a Humanoid Underwater Robot
Development and Control of a Humanoid Underwater Robot
2020 6th International Conference on Mechatronics and Robotics Engineering (ICMRE), Barcelona, Spain, 2020, pp. 6-11,
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Professor Siavosh Kaviani was born in 1961 in Tehran. He had a professorship. He holds a Ph.D. in Software Engineering from the QL University of Software Development Methodology and an honorary Ph.D. from the University of Chelsea.