29 "Wanli" Raspberry Pi car - straight-driving deviation problem and new control mode

lb8820265

29 "Wanli" Raspberry Pi car - straight-driving deviation problem and new control mode [Copy link]

This post was last edited by lb8820265 on 2022-3-20 10:32

The car finally moved successfully, but it was found that after the car made multiple parallel moves, the yaw direction would be biased. The main reasons for this phenomenon are:

1. When the car starts, not all wheels start at the same time, and there is a control dead zone;

2. When the trolley stops controlling, the wheels cannot stop immediately due to inertia, resulting in slight rotation.

Therefore, use the following method to solve it.

Setting up Quick Launch Control

When the motor starts from a stop, there is an obvious stall, and the stall amount is different for each motor. Therefore, to solve this stall problem, the motor can be controlled without a small amount, and the output of each motor can be divided by 2, and then added to 50, so that the minimum output is 50. The core code is as follows.

if ((int) speed1 > 0) {
speed1 = speed1 / 2 + 50;
} else if ((int) speed1 < 0) {
speed1 = speed1 / 2 - 50;
}

Use brakes instead of 0 control amount

When not controlled, the wheels will continue to rotate for a while due to inertia. The motor drive has a braking mode, which will quickly reduce the wheel speed.

In the Raspberry Pi code, it is mainly reflected in the execution of braking when receiving 0 control amount. The code is as follows.

float gen=2.55;
if(Data[0]>128){
M1.Motor_out=(256-Data[0])*gen;
M1.Direction=2;
}else if(Data[0]==0){
M1.Motor_out=0;
M1.Direction=3;
}

Added steering forward control mode

The Nam wheel car can also be controlled as an ordinary steering wheel control car, so there is no problem of steering caused by translation control.

The Y-axis value of the remote sensor is used to control the forward and backward movement of the car, and the X-axis value is used to control the steering. The main code is as follows.

void Tuenmode_mecanumRun(float ySpeed, float aSpeed)
{
float speed1 = ySpeed + aSpeed;
float speed2 = ySpeed - aSpeed;
float speed3 = ySpeed - aSpeed;
float speed4 = ySpeed + aSpeed;
}

question

The quick start method can start quickly, but it can only move forward, backward, left and right. It cannot move in the diagonal direction because the wheels need to stop turning.

Using brakes instead of 0 control will cause the car to stop quickly when the control is stopped, which can slightly reduce the rotation of the Yaw, but it will also cause the car to feel bumpy when it stops.

The forward and backward control method can control forward and backward at will, but oversteering often occurs, making control very troublesome.

Source code

GitHub:

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Gitee:

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