Final Simulation
The final simulation of the wheel-legged biped robot project was successful in achieving all the project goals, which were to control the balance of the robot, make it move forward and backward, turn left and right, and extend and retract while maintaining balance. The success of the project was achieved by designing a control system that uses PID controllers to control the robot's joints and ensure its stability. The project code was simplified by using subsystems and highlighting the main parts of the code to make it more organized and easier to understand. This allowed the project to focus on the main goals of the project without getting lost in the details of the code.
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The first goal was to control the balance of the robot, which is essential for any robot to perform effectively. Here, it successfully used PID controllers to maintain the correct position of the robot's shoulder and knee joints, which allowed the robot to remain in its normal mode without extending or retracting. This ensured that the robot was stable and able to move in the desired manner. The next step was to make the robot move forward and backward, which was achieved by controlling the speed and direction of the wheels. It was able to adjust the setpoint values and PID gains of the controller to achieve the desired movement while maintaining the robot's balance. Also, successfully achieved the goal of making the robot turn left and right by controlling the speed and direction of the wheels on each side of the robot. This was accomplished by adjusting the setpoint values and PID gains of the controller, which allowed the robot to turn smoothly while maintaining its balance.
Finally, the main goal of the project was to make the robot extend and retract while controlling its self-balance. This was accomplished by designing a control system that uses PID controllers to control the extension and retraction of the robot's legs while maintaining its balance. This allowed the robot to perform various movements, including move upward, move backward and moving. The wheel-legged biped robot project was successful in achieving all the project goals by using PID controllers to control the robot's joints and ensure its stability. The code was simplified and organized, which allowed the project team to focus on the main goals of the project. The robot is now capable of maintaining balance while performing various movements, which is a significant achievement in the field of robotics.
Forward and Backward motion
The forward and backward motion of the robot is achieved by controlling the velocity of the wheels. In a differential drive system, the robot moves by changing the speed and direction of the wheels. The left and right wheels of the robot are driven independently, and the difference in their speeds causes the robot to move in a straight line or turn.
In this project, the left and right wheel velocities were controlled using the gain values. The gain values are used in the PID controller to adjust the input values to the wheels to achieve the desired velocity. The sign of the gain values determines the direction of the motion. If the left wheel gain is positive and the right wheel gain is negative, the robot will move backward. Conversely, if the left wheel gain is negative and the right wheel gain is positive, the robot will move forward.
The gain values also determine the magnitude of the velocity of the wheels, which, in turn, determines the speed of the robot. A higher gain value will result in a faster speed, while a lower gain value will result in a slower speed. It's important to note that the gain values must be adjusted carefully to maintain the robot's balance and stability. A high gain value can result in unstable motion or even tipping over, while a low gain value can result in slow or unresponsive movement. Therefore, the gain values must be adjusted based on the robot's design and operating conditions to achieve the desired level of control and stability.
Turn left and Right
Turning is a crucial aspect of any mobile robot's motion control system. In the case of a wheel-legged biped robot, turning is achieved by manipulating the speed of the wheels on either side of the robot. This is accomplished by adjusting the gain values of the left and right wheels in the control system.
To make the robot turn left or right, the gain values for the left and right wheels are set to have opposite signs. If the left wheel gain is positive and the right wheel gain is negative, then the left wheel will rotate faster than the right wheel, causing the robot to turn right. Conversely, if the left wheel gain is negative and the right wheel gain is positive, then the right wheel will rotate faster than the left wheel, causing the robot to turn left.
It's essential to note that the magnitude of the gain values affects the turning radius and speed of the robot. A higher gain value results in a tighter turn and faster rotation, while a lower gain value results in a wider turn and slower rotation. Thus, the gain values need to be carefully adjusted based on the specific requirements of the robot's intended motion. This will ensure that the robot can turn efficiently and smoothly while maintaining balance.
In summary, turning in a wheel-legged biped robot is achieved by manipulating the speed of the wheels on either side of the robot. By adjusting the gain values of the left and right wheels, the robot can turn left or right with different turning radii and speeds. The gain values need to be carefully adjusted based on the specific requirements of the robot's intended motion.
Extending and retracting
The slider gain block in the robot control system is responsible for controlling the extension and retraction of the robot's legs. The block is an input block that allows the user to adjust the gain value with a slider input. The gain value determines the degree of extension or retraction of the robot's legs.
The slider gain block is connected to both the shoulder joint and knee joint of the robot. When the slider gain value is increased or decreased, the robot's legs extend or retract accordingly. However, when the robot is extending or retracting, its balance is likely to be disturbed. Therefore, to maintain the robot's balance, the values from the slider gain block and the joint sensors go through a sum/subtract block.
The sum/subtract block adds the values from the joint sensors to the values from the slider gain block when the legs are being extended and subtracts them when the legs are being retracted. This helps to maintain the balance of the robot while it is extending and retracting its legs. By adding or subtracting the values, the block adjusts the robot's balance and prevents it from falling over while its legs are in motion.
The slider gain block is an input block that controls the degree of extension or retraction of the robot's legs. To maintain the robot's balance while the legs are in motion, the values from the slider gain block and the joint sensors go through a sum/subtract block, which adds or subtracts the values accordingly to adjust the robot's balance. This allows the robot to extend and retract its legs while maintaining balance.
Final graph of balanced robot simulation
The PID controller values for the wheel-legged biped robot are shown in These values have been fine-tuned based on feedback from the scopes in Figure to achieve a desired response of the robot, which includes maintaining stability and reaching balance. The setpoint values represent the target position or speed of the wheels, which can be modified to perform different actions such as moving forward, backward, turning left or right, and extending or retracting the legs. If the wheels follow the setpoint values accurately, the feedback signals remain stable, indicating that the robot is able to maintain its balance.
In the context of a control system, the transient time response refers to the amount of time it takes for the output of the system to reach a steady-state value after a change in the input. In this project, the input command was a combination of velocity and height commands, and the robot was required to maintain balance while following these commands.
The controller's steady-state error refers to the difference between the desired output and the actual output of the system when the input is constant. In this case, the steady-state error was negligible, which means that the robot was able to maintain the desired velocity and height without significant error. This is a desirable trait in a control system, as it ensures that the system is accurate and precise.
The mild vibrations in the robot's tilt angle indicate that the robot experienced some oscillations in its motion. These oscillations could be caused by a number of factors, such as imperfections in the mechanical design or external disturbances. However, the fact that the vibrations were mild suggests that the controller was able to dampen these oscillations to some extent, which is another desirable trait in a control system.
The results of the transient time response analysis suggest that the robot is capable of maintaining its balance, controlling its forward velocity, and rejecting disturbance forces. These are important characteristics for a wheel-legged biped robot, as they allow the robot to move and operate in various environments and conditions.
The PID values for the shoulder and knee joints of the wheel-legged biped robot determine how these joints respond to changes in their respective setpoints. The PID controller is a feedback control system that uses three control terms: proportional (P), integral (I), and derivative (D). Each of these terms plays a role in determining the output of the PID controller, which is then used to adjust the position of the joint.
By adjusting the values of P, I, and D, the PID controller can be tuned to achieve optimal performance for the specific application. In the case of the wheel-legged biped robot, the PID values for the shoulder and knee joints were tuned to ensure that the joints responded accurately and quickly to changes in the setpoint, while also maintaining stability and reducing any steady-state errors or oscillations in the system.
Conclusion
The wheel biped robot project is a remarkable feat of engineering and innovation, combining the stability of a wheeled robot with the mobility and versatility of a bipedal robot to create a machine capable of navigating complex terrain while maintaining balance and stability. The project met all its objectives, starting with a simple self-balancing robot and progressing to a complex wheel biped robot that can perform various movements while maintaining balance. The project employed a multidisciplinary approach, combining Solidworks design and Matlab Simulink simulation to create a realistic simulation of the robot's behaviour. A comprehensive controller was developed, based on a dynamic model of the robot refined through system identification experiments, to achieve efficient posture and movement balance control. The simulation experiments demonstrated the effectiveness of the design in terms of stability and balance control. The WBR's potential applications in industries such as manufacturing, transportation, and exploration are significant. The project's success showcases the power of multidisciplinary engineering and collaboration, setting a high standard for future projects and opening up exciting possibilities for further innovations in this technology.