Abstract: Based on a brief introduction to the application background of Delta's electromechanical servo system in robotic arms, this paper discusses in detail the stability debugging of motion control systems based on field experience. The discussion process combines theory with practice and includes important principle analysis. Keywords: robotic arm, Delta servo, motion stability 1 Introduction Chemical arms for molding machines are mainly divided into two types according to their drive type: one is a low-end robotic arm driven by pneumatic components for low-speed point-to-point motion control; the other is a high-speed, high-precision positioning robotic arm that requires a high-performance servo system as the drive element. This paper discusses the second type, the electromechanical servo-controlled robotic arm, which is based on Delta servo system technology. The application of servo systems in robotic arms differs from general servo applications. For example, a customer uses a certain Japanese series of servo systems. Delta servo systems, through reasonable design, can achieve higher performance indicators while reducing customer costs and improving the cost-effectiveness of their products. 2 Delta Servo System Application Design 2.1 Process Requirements The process requirements of the robot arm are that the servo should run smoothly and stably during the positioning operation of the machine head. The running speed of the servo will determine whether the working efficiency of the robot arm can meet the application requirements of the customer. During high-speed positioning, the servo motor should not overshoot, oscillate, or have too long a settling time. All of the above requirements are achieved under the condition that the load inertia ratio is close to 70. High-performance servo system as the driving element for high-speed and precise positioning high-performance molding robot arm See Figure 1. [align=center] Figure 1 High-precision servo-controlled molding robot arm[/align] 2.2 Servo System The robot arm in this project is a single-axis structure robot arm. The basic hardware configuration is divided into control part and drive part. (1) Controller. The controller is a handheld control system developed by a microcontroller and adopts analog control servo driver. (2) Driver. Delta ASD-A0421LA servo driver + ECMA-C3060402ES servo motor, that is, the A+B configuration of Delta servo ASD-A driver and ASD-B motor. (3) Transmission structure. The transmission structure between the servo and the load adopts a 5:1 reducer and a T-tooth steel wire PU belt drive. (4) System block diagram. See Figure 2 for the block diagram design of the servo control system. [align=center] Figure 2 Servo control system block diagram[/align] 3 Servo motion stability debugging First, the load inertia ratio was estimated to be 68.6 using Delta debugging software. Under such inertia, to achieve high-speed response of the servo, the servo gain must be increased to ensure the control function of the servo. However, after adjusting the gain to a certain level, mechanical resonance will inevitably occur. As for the mechanical resonance point being captured by FFT software, it is found to be near the frequency of 189 Hz. Therefore, after setting the notch filter frequency to 189 Hz and the attenuation rate to 4 dB, the servo speed control gain can be increased to more than 5000 rad/s. However, even with this gain, the motor's operating characteristics are still poor. The motor oscillates repeatedly during positioning and cannot position quickly. The speed control gain must be increased further, but increasing the speed control gain causes current saturation, leading to further motor vibration. In this situation, the resonant low-pass filter and external interference resistance gain must be reduced. This increases the speed control gain to over 7000 rad/s. The servo can then position quickly and accurately, eliminating repeated oscillations. Figures 3 and 4 show curves captured in real-time by the ASD-A servo debugging software. Under these conditions, the servo's operation is not smooth. During acceleration, the motor accelerates at high speed. The servo runs at 1600 rpm, and then experiences a significant acceleration process in the middle, with the servo speed around 1000 rpm. This operating condition does not meet the customer's requirements. [align=center]Figure 3 Controller Speed ​​Command Curve 1[/align] [align=center]Figure 4 Motor Running Speed ​​Curve 1[/align] By observing the two curves (Controller Speed ​​Command Curve 1 and Motor Running Speed ​​Curve 1), it can be seen that the servo motor moves almost exactly according to the speed command from the host computer. However, why does this acceleration and deceleration process occur? Through communication and joint research with other engineers, it was found that due to excessive load inertia, the servo speed response is not fast enough, resulting in excessive speed error. Therefore, the servo is constantly performing integral tuning for the speed error. When the robot controller receives the servo encoder signal for position control, the integral tuning of the position error is very slow after the controller acquires the servo encoder signal, resulting in slow command processing speed. This causes fluctuations in the speed command and also makes the servo motor run unevenly and unevenly. To address this phenomenon, the servo speed integral compensation was adjusted to 0, so that the servo driver does not perform integral tuning for the speed error, resulting in smooth motor operation. At the same time, since the host computer performs position control, the positioning of the servo motor is not significantly affected. After reducing the speed integral compensation parameters, a significant change was observed in the curve, and the motor operation became much smoother. Figure 5 shows the waveform captured using a servo oscilloscope. Due to space limitations, a brief list of servo-related parameters is provided. [align=center] Figure 5 Control Command and Motor Speed ​​Curve 2[/align] 4 Conclusion The Delta ASD-A servo's performance, in extreme testing, completely surpasses that of a certain well-known Japanese servo system, achieving a maximum speed of 2800 rpm and a positioning settling time within 80ms. Throughout the entire 1800mm stroke, from initial acceleration to smooth operation and rapid positioning, the entire process, including the movement of the motor head, maintains high speed while remaining stable, demonstrating the servo motor's stable and smooth operation.