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Set point is always zero. When the bought leans forward the error goes positive when the bot leans backwards the error goes negative.

The Proportional gain can receive the number of degrees + or - from Zero (balanced) up to +-180° but I'm only using about +-20°. with my ideal Kp of 10 that provides an output of +-200 I'm sending to my motor controller. The PWM portion of the Arduino UNO can handle an input of 0 to 255. While my motors won't start till the PWM output reaches 30 that leaves me a total range of 0 to 225 (Shifted by 30) to be used to control the motors. Since we are not using integral to start with I will skip its explanation. Derivative is a time-based kicker. What I mean by Kicker is that it only alters the proportional output if change occurs. So, if over 1 second period the change 1 degree it will have a specific effect on the output 1 * Kd or 1 * .4 and .4 will be added to the output with the intent of dampening or enhancing the effect depending upon direction of travel towards setpoint. with my PID loop I divide the 1 second up by 100 and I do the same with the derivative so if there is a positive change I add to the proportional an opposite value added to the output nullifying the rate. And the change in degrees while trying to achieve balance is much higher than .4 degrees in a second. This could be somewhere in the hundreds of degrees in a second. So, .4 has a much higher influence on the output. Now remember when you are balanced you should have little to no rate of change and so derivative is at or near zero.

The proportional gain should have units similar to output/degree error. The derivative gain should have units of output/rate of degree of error. The integrator should have units of output /(degrees of error * time ) The output seem have little resolution in your case which has a usable range of 30-255. The output units need to be converted to torque. There are plenty of documents on how to control a Segway two wheel robot. These documents will have formulas involving torque inertia and angular acceleration. Simply put torque/inertia=angular acceleration although the necessary formulas are much more complicated than that. For tuning look for pole placement.

the arduino PWM receives a byte a number between 0 and 255 this in turn adjusts the PWM value sent to the H-Bridges which provide a pulsed signal directly to the motors below 30 the motors do nothing due to the resistance in the gearing of the bot. for most Arduino balancing bot programmers this causes the biggest issue in getting there little bots to balance. You are right there is allot more to PID than what I've showed or mentioned and you could get into much detail just not in 2 minutes. Thanks for your post

When the input from the gyro goes negative (based on setpoint) I reverse the H-Bridge then provide a positive value again to the Drive and the motors power up in reverse

Ashish Jog assuming that you know that the output is error+integral+derivative. Ki kp and kd are just Values multiplied by each term. Think of the as scale factors. The end equation is more like (kp*error)+(ki*proportional)+(kd*derivative)

Decrease your kp in half. And describe the results

It has 2 phases while I change the kP. First, it has low respond when trying to balance, and second it supershaky and slam on the floor after the blink of the eye. :) I think it's because my PID program, here it is: int outMax = 255; int outMin = -255; float lastInput = 0; double ITerm =0; // PID constants double kp = 100; // Proportional value double ki = 0; // Integral value double kd = 0; // Derivative value double dInput; double Setpoint = 0; // Initial setpoint is 1.8 double output; // Calculates the PID output double Compute(double input) { double error = Setpoint - input; ITerm+= (ki * error); if(ITerm > outMax) { ITerm= outMax; } else if(ITerm < outMin) { ITerm= outMin; } dInput = (input - lastInput); // Compute PID Output output = kp * error + ITerm + kd * dInput; if(output > outMax) output = outMax; else if(output < outMin) output = outMin; // Remember some variables for next time lastInput = input; return output; } Thanks.

hey, I got it balance :). It's due to my motorControl code. :))) Now i'm trying to control it by an bluetooth module. But I have a problem again when I change the Setpoint to move the robot forward and backwark, it overshoot real fast and fall down. Do you have any idea about that?

yes I also use bluetooth, the same problem with you, is it not good to use bluetooth ??

what's wrong with its control code???

I found the RC Car at a thrift store for a couple bucks, It's a JLX Overdrive johnny lightning land water rc car. It was missing the controls and batteries. turned out to be perfect for a balancing bot. I'm not sure what motors it uses or the over gear ratios. I don't dare tear it apart to find out, I may not get it back together :)

I had a detailed discussion in the Arduino forum on balancing bots. I have the code at post #50 as attachments. I have made several improvements and changes that have come about and I will post the sketch somewhere when they are ready :) and I will comment of there location here on your post when I do. forum.arduino.cc/index.php?topic=397918.msg2829907#msg2829907

I had a detailed discussion in the Arduino forum on balancing bots. I have the code at post #50 as attachments. I have made several improvements and changes that have come about and I will post the sketch somewhere when they are ready :) and I will comment of there location here on your post when I do. forum.arduino.cc/index.php?topic=397918.msg2829907#msg2829907

i love and appreciate your work... but i just want to balance my robot with enocder... do not want to throttle it...as u done...