The Steering Gear Positioning Accuracy Adjustment Method Teaches You How To Solve The Problem Of The Steering Gear Not Rotating In Place.

The most troublesome thing about playing withservos is not being able to adjust the accuracy properly. Obviously a lot of programs have been written and the hardware has been checked several times, but theservoeither doesn't turn in place, or it keeps making a "click" sound. In fact, inaccurateservopositioning is a problem that many novices and even veterans will encounter, but don't worry, in most cases it's not that the hardware is broken, but that you haven't found the way. Today we are going to talk about how to understand the accuracy of the steering gear.

What affects the accuracy of the steering gear?

Many people focus on the servo itself from the beginning, but they do not know that the factors that affect accuracy are actually a set of "combination punches". Unstable power supply is the number one killer. Once the voltage fluctuates, the position of the servo will be erratic. Secondly, there is a mechanical virtual position on the steering wheel, that is, the gap between the gears. Although this situation cannot be completely eliminated, it can be minimized. In addition, the control signal you gave, the frequency and resolution of the PWM (Pulse Width Modulation) wave are fine enough. If you want to adjust the accuracy, you have to investigate these sources one by one. This is just like debugging a sound system. All aspects of speakers, power amplifiers, and sound sources must pass the test.

When debugging the servo accuracy, many people only focus on the servo itself. But in fact, there are many factors that affect accuracy. Unstable power supply has a great impact on accuracy. As long as the voltage fluctuates slightly, the position of the servo will drift out of control. Furthermore, there is the mechanical virtual position of the steering wheel, which is the gear gap problem. It cannot be completely eradicated, but its impact can be reduced as much as possible. In terms of control signals, the frequency and resolution of the PWM (Pulse Width Modulation) wave are also crucial. In order to accurately adjust the servo accuracy, you must check these sources one by one, just like adjusting the audio. The speakers, power amplifiers, and sound sources must all be in good condition.

How to choose a suitable power supply for the servo

The power supply thing really needs to be talked about. If you are using a USB power supply or a battery box that costs a few yuan, the voltage will drop drastically and the servo will definitely fail. When choosing a power supply, first ️1.Look at the rated voltage.The general nominal voltage range of the servo is 4.8V to 6V. Try to choose a 6V regulated power supply so that the power is sufficient and stable. Secondly️2.Calculate the current.Don’t just look at the average current, but the locked-rotor current. When a medium-sized servo is locked, the current may soar to 1-2A. If you connect several servos at the same time, the power output must be doubled. It is recommended to use an adjustable power supply with a display or a branded switching power supply. You will feel at ease when you see that the voltage is stable and does not drop.

Why is your control panel not accurate enough?

Don't be so naive as to think that as long as it can rotate, it means the accuracy is sufficient. In fact, many entry-level control boards use 8-bit microcontrollers, and their internal PWM resolution may only be 8 or 10 bits. What exactly is this concept? To put it simply, 180 degrees is divided into 256 or 1024 parts. In this way, the angle change corresponding to each part is relatively large. If you expect the servo to accurately rotate 0.1 degrees, this control board simply cannot send out such a fine pulse signal.

In this case, you need to carefully consider replacing it with a 32-bit high-performance main control chip, or connecting an external high-precision PWM drive module to increase the resolution to 12-bit or even 16-bit. Only in this way, the servo will appear smooth and smooth during fine-tuning operations.

How to fine-tune the servo angle through the program

The hardware is in place, and the software is the soul. During the programming process, do not rigidly follow the formula to calculate the PWM duty cycle. You know, there are actually subtle differences in the center position and stroke of each servo. At this point, all you need to do is️write the calibration program. First send an intermediate value, such as a 1.5ms pulse, to center the servo, and then use a screwdriver to physically adjust the servo arm so that it is roughly horizontal.

Then, gradually increase or decrease the pulse width value in the code, for example, increase it by 0.01ms each time, carefully observe whether the servo can be accurate, record the corresponding minimum pulse width and maximum pulse width values, and then write them to your library file. This is the so-called "one machine, one strategy".

How to install the steering wheel and connecting rod accurately

Sloppiness in the mechanical structure will make all your previous efforts in vain. When installing the steering wheel, be sure not to use brute force to knock it in, as the gears may be easily damaged. Before installing the screws, first turn on the power and let the servo run to the neutral position you want, and then install the steering wheel. Make sure that the steering wheel is horizontal or vertical at this time to reduce the initial deviation. The connecting rod should be as short and thick as possible, and avoid using soft and thin wire. If there is a gap in the joint, you can use a little hot melt glue or Teflon tape to fill it to minimize the amount of shaking.

How to make good use of the PID adjustment that comes with the servo

Nowadays, many high-end servos support PID parameter adjustment. This is like installing an intelligent brain on the steering gear. Among them, when P (proportion) is increased, the response speed will become faster, but jitter is prone to occur; I (integral) can eliminate static differences, but if it is increased, an (overshoot) situation will occur; D (differential) can predict the action, thereby making the movement smoother.

If you are using this type of digital servo, do not use the default settings. First, fix the servo so that it is in no-load operation, then slowly increase P until jitter appears, then adjust it back a little; add a little more I to eliminate the residual error; and finally add D to suppress rebound. This process requires a certain amount of patience, but once it is adjusted, the servo operates as silky smooth as if you had taken Dove.

Having said so much, in fact, adjusting the steering gear accuracy is a process of "seeing, hearing and asking". From power supply, control, software to machinery, no link can be missed. Is there any project you are currently working on that is stuck on the accuracy of the servo? You might as well talk about your specific situation in the comment area. Maybe everyone can come up with ideas and the problem can be solved. If you find this article useful, don’t forget to like and share it so that more friends who play servos can see it!