# Design and Implementation of Inverse Kinematics and Motion Monitoring System for 6 DoF Platform
## 6 Experimental Validation  
Figure 13 contains photographs of the four strokes under the control of 6 DoF. This section validates the accuracy and feasibility of the proposed method by using experimental results. Traditional inverse kinematics and the proposed inverse kinematics were written into the software--only the inverse kinematics software was modified, the hardware was not--to compare the motion of the six-axis crank arm platform when the two algorithms were applied. Then, 6 DoF commands were issued to the platform through the human-machine interface, and the movable range of each DoF was recorded. Figure 14a-c are records of the relevant measurement results. The controllable angles of the two algorithms were compared, as indicated in Figure 14a. Because the traditional method used the trial-and-error method to control the lower platform coordinate, when the calculated rod length approximated the actual rod length, the movement was completed. The traditional method allowed the actuator to be operated only within the linear region, that is, a position of 60 to 180 degrees. The proposed method opted to directly map the crank arm platform to the Stewart platform, enabling the actuator operating region to reach 50 to 230 degrees. A comparison of the algorithms is presented in Figure 14b, where the subscripts \"old\" and \"new\" denote the traditional and proposed methods, respectively. As in the figure, the movable range of the proposed method was larger than that of the traditional method--a front-back distance 60 mm longer, a left-right distance 80 mm longer, and a vertical distance 160 mm longer, which effectively improved the stroke of the platform operation space. The algorithms' controllable angles of rotation--known as roll, pitch, and yaw--were compared, as in Figure 14c. The angles of rotation of the proposed algorithm were wider than those of the traditional algorithm--8 degrees wider in roll, 4 degrees wider in pitch, and 4 degrees wider in heave. An enlarged operating angle implies an increased overall platform space. Figure 12a,b are the 2 DoF \(\pm\) 300 mm displacement  
Figure 13: The control of 6 DoF: (**a**) heave, (**b**) pitch, (**c**) roll, and (**d**) surge. response diagrams, where the motion control command begins at 8 s with a period of 4 s. To observe the relationship between surge and sway--a 90-degree difference--more clearly, they were plotted on the horizontal and vertical axes, respectively, forming a perfect circle (Figure 15b). Figure 16a-c present the displacement, velocity, and acceleration curves of surge conducting 150 mm of forward and reverse rotation, and the velocity was obtained using differential software. Platform operation involved complex mechanical parts as well as the simulator cab. Accordingly, a few spikes were observed in the differential velocity due to discontinuous displacement. Figure 17a,b are the response diagrams of the three translational DoF (surge, sway, and heave) at \(\pm\)300 mm displacement with an angular difference of 120 degrees between any two. Regarding heave, the laser light of the displacement meter hit the rear of the upper platform. Due to the unfavorable mechanism smoothness, ripples were observed in the extracted signals. A 3D circle was formed when the three translational DoF were spatially plotted. Figure 18a-d are the response diagrams of the three other DoF at \(\pm\)26 degrees with an angular difference of 120 degrees between any two. In Figure 18b, RS232 is used to read the angular velocity of the gyroscope, which has an amplitude of \(\pm\)12 degrees/s. The roll, pitch, and yaw were spatially plotted, forming a 3D circle. Figure 19 shows the x, y, and z axis accelerations of the test platform, and the impulse responses were captured by the accelerometer.