What does the control method of the steering gear mean? A thorough explanation

Have you ever thought about how those "small joints" that allow the wings of model airplanes to swing flexibly, and the "small joints" that allow robot arms to grasp accurately, understand human speech? In fact, the key core here is the steering gear. What you asked about"What does the control method of the steering gear mean?"What exactly does it refer to? Simply put, it is a language system used to issue "action instructions" to the steering gear.This language clarifies the angle to which the servo needs to be turned, how much strength and how fast to use to achieve the corresponding action.. If you don't understand it, then the servo will be just an expensive piece of metal that trembles slightly in your hands.

Primary stage: the never-ending signal line

The most commonly seen "language" is the PWM (Pulse Width Modulation) signal. You don't need to remember this awkward abbreviation, you just need to understand its core meaning - the magic of time. Imagine that there is a valve in front of you that needs to be precisely controlled. You can't twist it directly. You can only control "how long to be on" and "how long to be off" of a light switch to operate indirectly. This is exactly what PWM does.

Specifically for the servo, there is a signal line on it, which receives a high-level pulse every 20 milliseconds (that is, 50 times per second). The length of time the pulse lasts is the only instruction. When the duration is 1.5 milliseconds, the servo will stop smoothly at the middle position of 90 degrees. When the duration is 1 millisecond, it rotates to 0 degrees. When the duration is 2 milliseconds, it flips to 180 degrees.

> Keywords: PWM signal core

We use daily situations to deepen our understanding. When you drive into a narrow parking space, don't you have to adjust the steering wheel "a small amount of times"? If you adjust the steering wheel too much, you will hit the wall; if you adjust it too little, you will not be able to get in.The same is true for PWM control of the servo. By continuously fine-tuning the standard value of "1.5 milliseconds", it can stop at any desired position.. It's like using your voice to command a hard-of-hearing friend: "Go left, okay, stop! Go a little bit further to the left..." It's just that the servo responds much faster and can receive and execute 50 commands per second. Many entry-level robot joints and small side turrets use this principle. manykpowerThe basic model of Servo has very good compatibility with this PWM signal and has anti-jitter optimization, allowing novices to obtain a smooth operating experience.

Advanced Dialogue: When Angle Is Not Enough

Pulse width modulation is a great technique, but it has an inherent limitation of only talking about angles. It is like an instructor who can only shout "turn 45 degrees to the left" and "turn 90 degrees to the right."This is enough to deal with many situations, but what if you want the servo to be like a ballet dancer, not only to rotate to a specified position, but also to control the speed of rotation and the strength of the entire process?? At this time, you need a more advanced "dialect".

In this way, serial communication (such as UART, RS485, etc.) or CAN bus control are introduced. Don't be afraid, these terms are just different models of telephones. Their essence is the same: to establish a two-way conversation.

It's not a one-way street where "I give the order and you execute the operation and continue." You can ask the servo, "What is your current temperature? Is the voltage currently enough? Is there a problem? What's the load?" The servo can also respond to you, "The report tells you that I am stuck in the relevant position and the current is too large!" More importantly, you can send a string of super The instructions are complex and intertwined with many factors, "Use a relatively slow speed of 30 degrees per second, and within 5 seconds, rotate gently and smoothly to a position of 150 degrees. If it encounters a resistance of more than 5 kilograms in the middle, it will automatically stop and sound an alarm!"

This is multi-dimensional control of position, speed and torque. You are no longer the officer giving orders, but have become a conductor.

> Keywords: feedback mechanism closed loop

We imagine that there is an experienced engineer who is debugging a six-axis robotic arm.If he only uses PWM, then he needs to send commands to the six servos separately, fully expecting them to collide with each other at an uncontrollable speed at the same second.。However, when using serial communication, he can use one command to prompt all servos to operate together: Servo A starts from 0 degrees to 90 degrees, and the operating speed is 20°/s; No. B servo runs from 45 degrees to -30 degrees at a speed of 15°/s; No. C servo keeps the torque on standby... At the same time, all servos can feedback current and position information in real time. This is the core meaning of closed-loop control.kpowerServo's high-end product line is designed for complex industrial application scenarios that require precise collaboration and health monitoring. It is also designed for industrial and commercial application scenarios.

Argument by contradiction: What would happen if advanced controls were not used?

Let's use the process of elimination for now to see what the consequences will be if we avoid understanding these "control methods". Suppose you are now building an omnidirectional reconnaissance vehicle. The four wheels required for the chassis must be accurately matched. You purchased four powerful servos, but only used PWM for control. Once your car hits the road, you long for it to go straight ahead. Since each servo has a slightly different neutral position (also referred to as the angle corresponding to 1.5 milliseconds) when it leaves the factory, and the friction on the ground is also uneven, you will notice that the car always deviates from the route. You can only adjust the PWM pulse width repeatedly, "increase 0.02 milliseconds for the left front wheel, decrease 0.01 milliseconds for the right rear wheel..." This will undoubtedly turn into an endless nightmare. However, the group of people who know what is called "control mode" use the serial port to send instructions such as "all steering gear angles return to zero and the target speed reaches the same value", and the problem is solved in an instant. You see, without knowing the language, even making the machine travel in a straight line has become a mysterious and mysterious knowledge.

Revolutions in Timeline: From Brute Force to Wisdom

In earlier times (in the analog era), the servo was just a particularly obedient tool for fools. As long as you give it a PWM signal, it will "rush" in the target direction regardless of the cost. The speed is the fastest in all situations, and it will not stop until it hits the limit block and makes a "dong dong" sound. The advantage is that the response is very direct and simple, but the disadvantage is that it is very rough, consumes a lot of power, and can easily damage the gears.

In the mid-term (digital era), the servo showed some cleverness, although it was still based on the PWM principle. With the help of a faster microprocessor, it "impacts" toward the target position hundreds of times per second. It is not only more accurate, but also has stronger holding power and significantly enhanced execution power.

In the current era of smart buses, the servo has become a node in the information network. You can change its ID and set overload protection for it. You can also read its operation logs and adjust its operation curve in real time. You can even use a master controller to connect hundreds of servos in series so that they can communicate and collaborate with each other.kpowerServo's smart servo series already allows you to set the complex action sequence of each servo by dragging the slider in the software just like operating a computer folder.

Do you notice the problem? The control method has evolved, and that is the process in which the servo has evolved from being like a "muscle", to being like a "cerebellum", to being like a "sensory neuron". If you are still using PWM to control a smart bus servo, it is like shouting at it in English that a mule cannot understand. This is an extremely serious resource misallocation and communication barrier.

Q/A FAQ

Q: Will the servo be burned if the PWM signal line is connected reversely?

In the case of A, this situation will occur. If the signal line is connected to VCC or GND, if the situation is mild, there will be no response, but if the situation is serious, it will cause the internal driver chip to be burned. This is the case.

Q: How to determine which control method my servo supports?

As far as A is concerned, check the product specification and count the pins. There are three lines, namely VCC, GND and signal. In this case, it is PWM, and the two extra lines, namely RX and TX, usually support serial communication.

Q: What is the reason for using PWM to control servo vibration?

A: There is signal interference or insufficient power supply. First, power the servo separately, and then connect the signal wires with short and thick wires.

> Keywords: fault-tolerant design thinking

I leave you with a question to think about. Today you understand that the "control method" is the protocol for communicating with the servo. However, the real controller always reserves a fault-tolerant mechanism during system design. For example, when the servo performs a dangerous action, not only does there exist "electronic limits", but you also add "physical limits" to the mechanical structure. When communication between software may crash, you design a hardware-level watchdog circuit.Understanding the control method is the starting point for playing with the servo, but judging in advance the scenario where the control method will fail is the dividing line between players and experts.。

The action advice is very straightforward: immediately "verify" the steering gear you have on hand. Check its data sheet to confirm the type of control signals it accepts by default. If it is a PWM servo, try angle control; if it is a smart servo, download the official PC software and try to modify the ID, read the temperature and set the operating curve. Sending a line of instructions in person is more productive than reading thousands of words of theory. The tacit understanding between you and the steering gear starts from your respect and understanding of this "communication code".