# Research on Kinematics Analysis and Trajectory Planning of Novel EOD Manipulator
## 2 Mechanism Design  
The main purpose of the robotic arm is to complete the two actions of grasping and placing explosives to realize the demolition of explosives [11]. The explosive disposal robot designed in this paper carries an explosion-proof device that can resist 400 g TNT. It needs to be equipped with a mechanical arm to place the explosives directly. In view of the mismatch between the ordinary manipulator and the mobile chassis and the problems of poor flexibility and low precision in the complex special explosive removal process, a new 5-DOF manipulator is proposed in this paper. To ensure the stability, reliability and flexibility of the manipulator, the choice of the number of degrees of freedom is particularly important when designing the mechanical structure. Because the manipulator is in-stalled on a mobile platform, the mobile platform can flexibly change the working position of the robot relative to the dangerous object, which is equivalent to a degree of freedom of rotation of the operating arm. Common industrial manipulators generally have 4-6 DOF. The higher the degree of freedom, the more flexible the manipulator is, but the greater the number of degrees of freedom, the more difficult it is to control the manipulator. In order to reduce the difficulty of control and complete the task, we chose 5 DOF. Therefore, the manipulator adopts the configuration of 5 + 1 DOF (5 DOF of the manipulator motion, 1 DOF of the end gripper opening and closing). The joints corresponding to the 5 DOF are the waist joint, shoulder joint, elbow joint, wrist pitch joint and wrist rotation joint. The joint axis of the shoulder joint, elbow joint and wrist pitch joint are parallel, thus forming a redundant degree of freedom, which can effectively increase the flexibility of the mechanism and improve the obstacle avoidance ability of the manipulator [12]. The configuration diagram of the manipulator is shown in Figure 1. Because the manipulator arm has 5 DOF and the waist joint is installed on the mobile chassis, the remaining 4 DOF are equivalent to three arms. Before the design, we also referred to the design parameters of ABB, YASKAWA and KUKA manipulators. Suppose the distance from the shoulder joint to the elbow joint is L\({}_{1}\), the distance from the elbow joint to the wrist pitch joint is L\({}_{2}\) and the distance from the wrist pitch joint to the end-effector is L\({}_{3}\). It is preset that the dead weight of the mechanical arm is 50 kg, the arm extension is 1.1m and the clamping weight is 5-10 kg. In this case, L\({}_{1}\) + L\({}_{2}\) + L\({}_{3}\)\(\approx\)1.1 m. The numerical values of L\({}_{1}\), L\({}_{2}\) and L\({}_{3}\) determine the working space of manipulator. In order to expand the working space of the manipulator as far as possible and reduce the working blind area, L\({}_{3}\) should be as small a value as possible, and the difference between L\({}_{1}\) and the L\({}_{2}\) should be as small as possible. At the same time, considering the dimensions after folding, the length of each part is set as follows: L\({}_{1}\) = 0.5 m, L\({}_{2}\) = 0.37 m, L\({}_{3}\) = 0.30 m.  
The foldable 5-DOF manipulator designed in this paper is applied to EOD robots as shown in Figure 2[13]. It contains 5 DOF, the manipulator arm span is up to 1.32 m and each joint is driven by a DMKE brushless servo motor. The clamping weight is 10 kg in the folded state, and the clamping weight is greater than or equal to 5 kg and less than 10 kg when fully expanded. Considering the safety factors, the servo motor with brake function is selected as the driving device from the waist joint to the wrist rotation joint of the manipulator, which will stop at the original place after power failure. In addition, the ultrasonic sensor is used as the limit sensor to limit the angle of each link when the manipulator is reset, so as to realize the automatic reset function of the manipulator and ensure its operation stability. Considering many factors, we adopt a HC-SR04 ultrasonic sensor.