# Design and Testing of Torveastro: An Outer Space Service Robot
## 6 A Dynamic Simulation  
With the dimension's parameters, a 3D CAD has been created to detail the component of Torveastro that allows it to perform the necessary movement while shielding the actuation, control, and electronics from the elements and keeping the design as compact as possible. Figure 8 illustrates the finalized Torveastro CAD, while Figure 8a shows the motor unit in detail. The motor unit, which has three actuators to control the arm's three DoF, represents the shoulder of Torveastro's anthropomorphic arm. The motor unit consists of two components. The first component is joined to the frame of the body and includes an actuator; this actuator is directly coupled to the second component, enabling it to spin 360 degrees. The second component of the motor unit has two actuators, one of which moves the cable-driven arm and the other, the cable-driven forearm. Both actuators move the two pulleys by bending and stretching precisely proportionately to the rotational direction. Figure 8b shows the limbs with their four components. The motor and arm, forearm, and end-effector are connected between each other by proper revolute joints. The motor unit interface permits the attachment of the limb to the motor unit. As previously stated, the arm and forearm are independently manipulated by two cables. The cables are routed via the arm and forearm bodies. A separate motor powers the two-finger end-effector at the end of the body. Figure 8c shows the prototype's entire construction. The planned prototype weighs around 50 Newtons. The ABS material from Table 1 has been selected for the simulations and prototype of [PERSON]'s prototype. With the entire CAD model and all of its attributes, an 8-s multibody simulation was performed to simulate a real-world operating scenario and evaluate the feasibility and behavior of the proposed motor unit characteristics. The results of the simulations are shown in Figure 9 and in Figure 10. As shown in Figure 9a, the shoulder is rotated 180 degrees forward and backward to return to its initial position. In addition, a flexion of the arm was simulated by applying an angular displacement of the corresponding elbow joint through cable actuation, as in Figure 9b, and a response torque of 2.80 N was applied at the same point to replicate the arm's total weight of 10 N carrying a payload of 90 N while pulling the cable. In addition, as shown in Figure 9c, the 100 N payload of the whole arm applied to the motor unit's edge. In the simulations, both body friction and earth gravity have been taken into account. Figure 7: A design scheme of the Torveastro prototype body with inside component location. Figure 10 shows the simulation results. Figure 10 displays the angular displacement given as input for shoulder actuation, while Figure 10 depicts the torque required to achieve the input motion. Between four and eight seconds, the motor starts to move from its initial position of zero degrees, reaches 180 degrees, and then returns to zero degrees. Figure 10 clearly separates the torque into two components: the component emerging from second 0.00 to 4.00, with a peak torque of 3.13 Nm at second 2.32. At second 4.00, the actuator of the shoulder joint reverses direction to return to the starting position, with the maximum torque of 5.07 Nm being reached at second 6.04. During the descent phase, a larger torque is produced to oppose the terrestrial gravitational pull and maintain the same motion profile. At 4.00 s, the motor that pulls the cable to simulate arm flexion is activated and satisfies the previously defined resistance torque. As seen in Figure 10, the actuator needed a maximum torque of 2.80 Nm to accomplish its intended function at second 8.00. As demonstrated in the graphs, the suggested method has a smooth behavior and may be implemented using commercially available intelligent actuators.