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| Automation block balanced motorcycle |
This series of articles document how my approximated automation-block PID controller works and how I implement them on self-stabilizing machines.
Proportional Controller on Bikes
For a motorcycle to self balance, a P controller is a must. A simple 2 sensor and reaction wheel will make a motorcycle oscillate badly.To build a vanilla self-balancing bike, the mechanism has to be small. I chose to fit this gyroscope system in the bike shown in the picture. As the spinning-block-powered contra-rotating gyroscope spins, the torque is canceled. However if the axes of rotation of the two gyroscopes are not aligned perfectly, a net torque is generated and increases as the angle between the axes of rotation gets bigger.
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| The two spinning blocks on steering hinges provides torque to balance the motorcycle, and the 2-anglometer angle tracker is synchronized with one of the 2 hinges. Another hinge is used to tilt the motorcycle |
The generated torque isn't linear to the angle, but sinusoidal. This is ideal when the angle is small. The output is approximately linear if the gyroscopes spin fast to provide enough torque at small angle differences. This makes it a P controller for tilt angle correction.
A note on this mechanism is that the gyroscopes themselves are strong enough to act as damper. Although the motorcycle still oscillates, with a bit of tuning it doesn't oscillate badly with the absence of term D. If it is a modded machine built with scaling, an active damper can be added.
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| Active damper, a D controller with 2-anglometer angle tracker and a reaction wheel |
Derivative Controller on Cars, and Fly-by-Wire Systems
If you know a little of cars and planes, you might know the idea of fly-by-wire systems. In this experiment, an angle tracker is on a steering block that mapped to the keyboard input. and the output mapped to the RTC steering system of the car. It creates a stabilized steering experience on drifty Besiege cars. The system corrects the over steering automatically.
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| Fly by wire steering, the car automatically flicks the wheel after power sliding |
Putting the tracker on another steering hinge/block that the user controls creates a fly-by-wire system. The gif below shows a VTOL test bed implemented with PD controller for pitch and roll, and a D controller for yaw. On this particular plane the user controls the nozzle vectoring for moving forward and backward. The roll and yaw are fly-by-wire.
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| PD stabilized system on Redstoneman's VTOL test bed |
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| The PD controller for angle used in the test bed above. Consists of a 2-anglometer angle tracker, a flying block pair and a reaction wheel |
Ekranoplan
Before jumping into hovering sci-fi vehicles, I'll introduce my Ekranoplan system.
It uses two P controllers for height to emulate the ground effect on each wing, and a P controller for height to change the lift from the propeller blocks and control the elevators. The system again does not have the D term. One is because I haven't found how to build a D controller back then, two is the drag from the aerodynamic blocks dampen the height change pretty well.
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| Ekranoplan test bed |
In the next article I'll show the choices i made to implement PD controllers into my hover car to efficiently deliver the performance I wanted.
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