Controlling the balance of a wheel-legged biped robot is a complex task that requires a series of calculations to ensure the robot remains stable and upright while in motion. Below are some of the key calculations needed for this type of control:

 

• Centre of Mass (COM) Calculation:

The first step in controlling the balance of a biped robot is to determine its centre of mass. This calculation involves finding the average position of all the mass in the robot. The centre of mass is important because it is the point at which the force of gravity acts on the robot. By keeping the centre of mass within the base of support (the area of ground contact between the wheels and legs), the robot can maintain its balance.

 

• Inverse Kinematics Calculation:

Inverse kinematics is the process of determining the joint angles needed to achieve a desired position of the robot's end-effectors (in this case, the wheel of the robot). This calculation is important because it allows the robot to move in a stable and controlled manner. By determining the joint angles required for each leg to maintain balance, the robot can adjust its posture to keep the centre of mass within the base of support.

 

• PID Control Calculation:

PID control is a common method used in robotics to regulate the motion of a system. This involves calculating the error between the desired position and the actual position of the robot, and using that error to adjust the robot's motion. The PID controller calculates the proportional, integral, and derivative components of the error and uses them to adjust the robot's velocity and position.

 

• Wheel Rotation Calculation:

The rotation of the wheels plays an important role in maintaining the balance of a wheel-legged biped robot. The rotational speed of the wheels must be carefully controlled to ensure that the robot does not tip over. The calculation for wheel rotation involves determining the speed and direction of each wheel based on the desired motion of the robot.

 

• Torque Calculation:

Torque is the force that causes rotation. In the case of a wheel-legged biped robot, torque is required to move the legs and rotate the wheels. The torque required for each joint and wheel can be calculated based on the desired motion of the robot and the mass distribution of the robot.

 

The calculations needed to control the balance of a wheel-legged biped robot involve determining the centre of mass, calculating the inverse kinematics, implementing PID control, determining wheel rotation, and calculating the torque required for each joint and wheel. These calculations allow the robot to adjust its posture and maintain its balance while in motion.

 

A PID (Proportional-Integral-Derivative) controller is a type of feedback control algorithm that adjusts the output of a system based on the error between the desired set point and the measured output. It is commonly used in control systems to achieve desired outcomes, such as maintaining balance in a robot.

  

The proportional gain (Kp) is used to adjust the output based on the current error. A higher value of Kp will result in a larger output for a given error, and therefore a faster response. The integral gain (Ki) is used to adjust the output based on the past error. The derivative gain (Kd) is used to adjust the output based on the future error. By tuning the gains (Kp, Ki, and Kd) appropriately, a PID controller can be used to achieve stable control of a system. In the case of a robot maintaining balance while changing height, the tilt angle error is used as the input to the PID controller, and the output is used to adjust the height of the robot to maintain balance.