Robotic joint design by agonist and antagonist arrangement with twisting small-diameter round-belts

Abstract

This paper develops a novel robotic joint mechanism by means of twisting a small-diameter round-belt, which enables slow movements of joint rotation unlike direct-drive actuator mechanisms. The actuator mechanism proposed in this manuscript is composed of two small-diameter round-belts located near the joint with opposite configurations. The two round-belts are twisted by DC motors placed on a motor stage, which can be activated by a step motor. This novel mechanism realizes movement of the robotic joint around its axis due to contraction forces generated by twisting both round-belts. That is, these round-belts act as agonist and antagonist actuators for the robotic joint, which give a human-like compliance to the rotational motion of the joint. Experimental results using the proposed one-link robot show that a high position resolution of the joint control can be achieved by increases and decreases in the amount of twisting. In addition, we clearly indicate a linear relationship between twisting and the joint angle of the robot. Finally, this paper reveals that the antagonistic twist-actuator system has a secondary role as a gear reducer that is capable of largely decreasing the velocity of joint movement.

Electromagnetic and thermal analyses of surface‐mounted permanent magnet motor with flux‐absorbing structure for enhancing overhang effect

“…With regard to the copper loss, it is the dominant component in this type of high-torque and low-speed application. In this case, this value can be calculated by (1). The copper loss causes a rise in the coil temperature, which increases the coil resistance according to (2) while also increasing the copper loss progressively…”

“…In (1) and 2, R s , I s,rms , R s0 , α, T, and T 0 represent the resistance of the winding, the phase current in root mean square (RMS) value, the resistance at the reference temperature, the temperature coefficient of the copper, the coil temperature and the reference temperature, respectively. Table 3 shows the copper loss at 20°C was reduced by 9.9% from 14.2 W in the SPM motor without the FAS to 12.8 W with the FAS.…”

“…Recently, the demand for collaborative robots has increased worldwide due to the high productivity and flexibility of these devices with a focus on smart factories and factory automation [1][2][3]. In the design of the robot joints, the driving module for collaborative robots must be designed with high-torque and power densities as well as compactness due to the limited work space [3,4].…”

Electromagnetic and thermal analysis and design of a novel‐structured surface‐mounted permanent magnet motor with high‐power‐density

“…The resistance values for conduction in Fig. 3 can be calculated by (1), where l i (m), k air (W/m °C), and A i (m 2 ) are the distance between the conductive material, the thermal conductivity of air, and the contact area, respectively. The l i varies according to the contact condition.…”

“…Robot is one of the core technologies of what is referred to as the fourth industrial revolution. Recently, the demand for the manufacturing of collaborative robots has increased dramatically [1][2][3][4]. Compactness is an important constraint in the manufacturing of a collaborative robot due to the limited work spaces of robots.…”