Analysis and Simulation of the Dynamics of Nickel Anode Plate Handling Robot

Corresponding Author: Guoping Li Mechanical Engineering, University of Jinan, Jinan, China Email: me_ligp@ujn.edu.cn Abstract: As an integral part of the industrial automation system, a joint robot with artificial intelligence technology, virtual prototype technology and co-simulation technology has developed rapidly. In particular, the development of coordinated control technology makes the robot trajectory tracking control advance in the direction of higher precision and higher efficiency and makes the whole robot system has high fitting human nature, high universality, high scalability and so on. In this study, for the structural characteristics of the nickel anode plate handling robot, a three-dimensional model of the handling robot was drawn using SolidWorks 3D design software. The linkage coordinate system of the robot is established by the D-H method. The dynamics model of the nickel anode plate handling robot was established using the Lagrange method and dynamics analysis was carried out. The simulation model of the robot was constructed based on ADAMS simulation software and the dynamics simulation was carried out to obtain the force curves of the joints. It lays the foundation for further optimization of the structure design and control system design of the handling robot.


Introduction
Nickel has excellent mechanical properties and corrosion resistance, high thermal conductivity and conductivity, low gas content and low steam pressure. It is used in food processing equipment, salt refining equipment, mining and marine mining. It is also mainly used in electronic products, high-precision chemical instruments and other products; Handling materials is an important link in industrial production, especially when the materials are heavy and toxic. The workers handling materials will be inefficient and inefficient cause certain harm to the body. To effectively solve this phenomenon and save labor, handling robots came into being.
As important automation equipment in the modern manufacturing industry, the application of handling robots is becoming more and more widespread and the development of handling robots is becoming more and more rapid. In the research and design process of handling robots, the theory and application related to robot dynamics are getting more and more attention. Theoretical analysis of handling robot dynamics can improve the stability and accuracy of the control system. Meanwhile, dynamics simulation is beneficial to optimize the structural design of robots and evaluate and check the dynamics characteristics of existing robot structures (Xu, 2007;Yi and Xue-Ping, 2009).
At present, the Newton-Euler method, Lagrangian method and Kane method are the main methods to study robot dynamics. For example, some researchers have applied ADAMS software to simulate the tracking trajectory in the space near the maximum load of the robot (Wang et al., 2017); some researchers have applied MATLAB software to analyze and simulate the dynamics of the simplified model (Liu and Hu, 2013;Zeng and Li, 2014). The dynamics simulation of the robot by applying these methods verifies the rationality of the structural design or the correctness of the theoretical calculation. In this study, we take the nickel anode plate handling robot as the research object, establish the dynamics model of the handling robot and use ADAMS to plot the simulation curve to verify the correctness of the dynamics model.

Overall Solution Design
The 3D model of this handling robot was created by SolidWorks, as shown in Fig. 1. It consists of a base, a large arm, a small arm, a wrist and a nickel anode plate fixture. In practice, the nickel-anode plate fixture is fixed at the end flange of the wrist, so the wrist end flange and the nickel-anode plate fixture are considered as a whole. The 6 degrees of freedom of the handling robot are :1, rotation of the base 2, pitch of the large arm 3, the pitch of the small arm 4, rotation of the front of the small arm 5, pitch of the wrist 6 and rotation of the nickel anode plate fixture. The first three rotational joints of the handling robot determine the position of the nickel anode plate fixture and the last three rotational joints determine the attitude of the nickel anode plate fixture (Hu et al., 2016).

Establishment of Connecting Rod Coordinate System
In order to elaborate the connection between the end position of the nickel-anode plate fixture of the handling robot and each joint angle, the theoretical knowledge of D-H was applied to construct the reference coordinate system of the handling robot (Zeng et al., 2010) and the results are shown in Fig. 2. Here, the origin O6 of the tool coordinate system of this robot is defined as the end position point of the robot and the base is regarded as linkage O0.

Establishment of Lagrange's Equation
There are various methods to solve the kinetic equations of the nickel anode plate handling robot, while the Lagrangian analysis method is based only on the energy term and enables the derivation of the kinetic equations in a simpler form. For the complex configuration of the designed nickel anode plate handling robot, the Lagrangian method is used to analyze the robot dynamics (Cui, 2013;Li and Zhao, 2008).
Let the turning angle variables of the six joints of the robot be: Let the driving torque of each robotic arm joint be:   1 2 3 4 5 6

T= T T T T T T
The kinetic energy of the robot linkage is: where: Uij, Uik -derivatives of the transformation matrix with respect to the joint rotation angle.
Ji and Ii -are the inertia matrix and the rotational inertia of the actuator.
Since the potential energy of the robot connecting rod is the sum of the potential energy of all the rods, the potential energy of the connecting rod can be expressed as: where the matrix of is composed of the projections of the gravitational acceleration of the connecting rod in the x, y and z directions:  The collation is shown below:

Nickel Anode Plate Handling Robot Dynamics Simulation
ADAMS is used to simulate and analyze the motion of the nickel-anode plate handling robot and the 3D model of the nickel-anode plate handling robot is created using SolidWorks software. The overall simulation model of the nickel-anode plate handling robot is shown in Fig. 3.

Adams-Based Dynamics Simulation and Analysis
After running the simulation according to the established simulation scheme, the simulation results were obtained as shown in Fig. 4 to 10.
The angular displacement variation curve in Fig. 4 shows that the curve of spline interpolation is smoother and smoother and the movement ends with each joint returning to the initial position without error. The velocity variation curve of Fig. 5 shows that the curve of cubic polynomial interpolation is smoother, but the maximum velocity of spline interpolation is smaller while satisfying the working need. The angular velocity change curve in Fig. 6 shows that the cubic polynomial is not only less smooth and continuous than the spline interpolation, but also the maximum values of angular velocity and angular acceleration are larger than the spline interpolation. The change of angular acceleration in Fig. 7 is curvilinear, while that of the cubic polynomial is linear, which indicates that the motion of the sample interpolation is smoother. The force curve in the z-direction in Fig. 8 is gentler compared with the cubic polynomial. The cubic polynomial is more intuitive to observe that the robot is almost in the same position from 2s to 4s and there is almost no up and down movement, which requires high rigidity of the robot and the sample interpolation process is easier to achieve. The curve change of spline interpolation is more moderate and the maximum moment is smaller than cubic polynomial interpolation. The curve changes of both methods are more gentle. Both return from zero kinetic energy to zero kinetic energy; both can satisfy the motion process, but the maximum kinetic energy of Fig. 10 is in the base frame, which is less harmful to the body of the nickel anode plate handling robot Table 2.

Conclusion
Based on the three-dimensional model of the nickel-anode plate handling robot with SolidWorks software and using the D-H method to establish the linkage coordinate system and the linkage parameters, the kinetic model is solved by the Lagrangian method in this study. Based on the three-dimensional model of the nickel-anode plate handling robot, the dynamics of the robot is simulated using ADAMS software and the driving torque of each joint and the motion of the nickel-anode plate are obtained in this study. Adams dynamic simulation is of great significance to the practical application of the handling robot. The handling robot solves the problem of difficult handling of heavy objects and harmful substances with certain specifications in actual production and improves the production efficiency.