3.2. Simulation Parameter Setting
After the model is simplified, the initial conditions and the material of each part are set according to the actual parameters of the prototype, as are the moving and rotating subsets for the model according to the motion, as shown in
Table 3.
In the process of loading, the mass of substrate soil in the handcart will gradually decrease as the turning angle increases. To simulate the process of substrate dumping, a variable force is applied to the handcart, the direction is always kept vertically down, and the initial value is equal to the gravity of 0.14 m3 of substrate soil, which is 1078 N. When the tipping angle of the handcart is less than or equal to 50°, the magnitude of the variable force is 1078 N (indicating the state of full soil); when the tipping angle of the handcart is greater than 50°, the size of the variable force decreases according to the cosine law (indicating that the substrate soil in the handcart begins to dump).
3.3. Analysis of Simulation Results
The simulation was run with a step size of 500 and a simulation time of 10 s. After the simulation was completed, the change curve of the flip angle, velocity, acceleration, angular velocity, and pushrod thrust in the process of feeding the overturning frame was obtained (
Figure 9,
Figure 10,
Figure 11,
Figure 12 and
Figure 13).
The change curve of the turning angle of the overturning frame and the handcart during the loading process is shown in
Figure 9. From 0 s to 6.66 s, the overturning frame moves along the straight track at a constant speed, and the turning angle is always 0°. From 6.66 s to 8.40 s, the front track wheel of the overturning frame enters the circular track; the overturning frame moves at a variable speed and the turning angle slowly increases from 0° to 34°. From 8.40 s to 8.60 s, the overturning frame turns around the front track wheel and the turning angle increases rapidly from 34° to 50°; from 8.60 s to 9.94 s, the overturning frame continues to turn around the front track wheel while the substrate is removed from the bucket truck. In 8.40 s to 8.60 s, the overturning frame rotates around the front track wheel, and the overturning angle increased rapidly from 34° to 50°; in 8.60 s to 9.94 s, the overturning frame continues to rotate around the front track wheel, while the subsoil is discharged from the bucket truck, and the overturning angle increases from 50° to 110°.
The horizontal acceleration change curve and horizontal velocity change curve of the overturning frame and handcart are shown in
Figure 10. From 0 s to 6.66 s, the horizontal velocity of the overturning frame remains unchanged at 68.9 mm/s; from 6.66 s to 8.40 s, the horizontal acceleration of the overturning frame shows several small abrupt changes, among which the biggest change is from 734 mm/s
2 to 1405 mm/s
2. Since the acceleration direction is generally positive, the horizontal velocity of the overturning frame increases from 68.9 mm/s to 225.9 mm/s; in the period from 8.40 s to 8.60 s, the horizontal acceleration of the overturning frame has several large abrupt changes. The largest abrupt change is from −7004 mm/s
2 to 7458 mm/s
2; an the abrupt change in the horizontal acceleration makes the horizontal velocity of the overturning frame to have many large abrupt changes. The largest of which was from 62.1 mm/s to 402.4 mm/s. In 8.60 s to 9.94 s, the horizontal acceleration of the overturning frame showed several small abrupt changes, the largest of which was from 3760 mm/s
2 to −1760 mm/s
2, and the horizontal velocity increased from 411.9 mm/s to the maximum value of 626.6 mm/s.
The variation curves of the vertical acceleration and vertical velocity of the overturning frame and handcart are shown in
Figure 11. In the period from 0 s to 6.66 s (the first stage), the vertical direction velocity of the overturning frame remained unchanged at 114.6 mm/s; in the period from 6.66 s to 8.40 s, the vertical direction acceleration of the overturning frame showed several large abrupt changes, the largest of which was from −9591 mm/s
2 to 1567 mm/s
2. The abrupt change in the vertical acceleration results in a multitude of minor fluctuations in the vertical velocity of the overturning frame. Because the acceleration direction is positive, the vertical velocity of the flipper increases from 114.6 mm/s to 371.6 mm/s and then decreases to 341.7 mm/s. In the period from 8.40 s to 9.94 s, the vertical acceleration of the flipper shows several large abrupt changes, the largest of which is from −2821 mm/s
2 to 6433 mm/s
2. The overall trend of acceleration changed from positive to negative, so the vertical velocity first increased from 341.7 mm/s to the maximum value of 541.6 mm/s, and then decreased to the minimum value of −13.9 mm/s, with a large range of vertical velocity change.
The change curves of the angular velocity of the overturning frame and handcart are shown in
Figure 12. From 0 s to 6.66 s, the angular velocity of the overturning frame remained constant at 0 rad/s; from 6.66 s to 8.40 s (the second stage), the angular velocity of the overturning frame increased from 0 rad/s to 0.56 rad/s and then decreased to 0.52 rad/s; from 8.40 s to 8.60 s, the angular velocity of the overturning frame showed several large abrupt changes, the largest of which was from 0.52 rad/s to the maximum value of 1.04 rad/s. In the period from 8.60 s to 9.94 s (the third stage: subsoil sliding stage), the angular velocity of the overturning frame showed several small changes, with an overall change from 0.62 rad/s to 0.98 rad/s.
The change curve of the pushrod thrust during the motion is shown in
Figure 13. In the period from 0 s to 6.66 s, the overturning frame moves at a constant speed and the pushrod thrust is constant at 1476 N; in the period from 6.66 s to 8.10 s, the front track wheel of the overturning frame begins to enter the circular arc section of the track, and the force arm of the pushrod thrust decreases rapidly relative to the force arm of the gravity on the overturning frame, the subsoil, and the dump truck, so that the pushrod thrust increases from 1476 N to 4426 N. In the period from 8.10 s to 8.40 s, the front track wheel of the overturning frame is about to move to the end of the circular arc section of the track, and the force arm of the gravity decreases compared with the force arm of the thrust. The arm of gravity decreases compared with the arm of thrust, so the thrust of the pushrod decreases from 4426 N to 4088 N. In the period from 8.40 s to 8.60 s, the overturning motion of the overturning frame is carried out, and the thrust of the pushrod changes abruptly from 4088 N to 7460 N because its support wheel is off the track; in this stage, the pushrod thrust reaches the maximum value of 7800 N, while there are several large abrupt changes, the largest of which is from 5044 N to 7800 N. From 8.60 s to 9.94 s, the required pushrod thrust starts to decrease because the mass of the subsoil in the handcart starts to decrease.