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Adding content to robot arm

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Sharwin Patil 2025-01-20 22:11:15 -06:00
parent 784fd7ca08
commit c9a69e022c
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content/posts/robot-arm-edu/index.md
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@ -19,6 +19,52 @@ An educational kit designed to teach the fundamentals of kinematics and dynamics
## Kit Design
The entire kit is composed of 3D printed parts, and off-the-shelf hardware/electronics. Students can assemble the kit without any soldering and with minimal tools.
<div align="center">
<img src="assembly_instructions.png" alt="Assembly Instructions" style="border-radius: 15px;">
<div align="center" style="display: flex; flex-wrap: wrap; justify-content: center; gap: 15px;">
<img src="step_1.png" alt="First Step of Instructions" style="border-radius: 15px; width: 45%;">
<img src="pcb_instructions.png" alt="PCB Instructions" style="border-radius: 15px; width: 45%;">
<img src="base_instructions.png" alt="Base Assembly" style="border-radius: 15px; width: 45%;">
<img src="full_assembly_instructions.png" alt="Full Assembly" style="border-radius: 15px; width: 45%;">
</div>
The instructions are laid out in simple steps, akin to LEGO instructions. A custom PCB was developed to simplify the wiring process and off the shelf stepper motors and drivers were used for easy integration with the Arduino microcontroller.
<div align="center">
<img src="students_building.png" alt="Students Building Kit" style="border-radius: 15px;">
</div>
## Software
In order to control the robot arm, a custom library was written in C++ to handle the microstepping. The library followed the same technique as the AccelStepper library to enable concurrent motion of multiple motors at a time in addition to applying acceleration and velocity profiles. A custom library meant students could easily write and implement their own motion profiles without having to deal with the hardware specifics.
```cpp
void LinkStepperMotor::computeNewPulseInterval() {
// Acceleration curve is split into 3 parts: acceleration, steady-state, deceleration
int totalSteps = abs(this->targetPosition - this->previousTargetPosition);
int stepsRemaining = this->getStepsRemaining();
int stepsCompleted = totalSteps - stepsRemaining;
int n1 = totalSteps / 3;
int n2 = 2 * n1;
uint16_t speedSPS = this->currentSpeedSPS;
// Determine which range we are in to apply the correct part of the acceleration curve
if (stepsCompleted <= n1) {
// Acceleration
// a(n) = k * n1 + a0
// v(n) = 0.5 * k * n^2 + a0 * n + v0
speedSPS = (0.5f * this->accelerationRate * pow(stepsCompleted, 2)) + (this->initialAcceleration * stepsCompleted) + this->initialSpeedSPS;
} else if (stepsCompleted >= n1 && stepsCompleted <= n2) {
// Steady-state
// a(n) = a_max = k * n1 + a0
// v(n) = (k * n1 + a0) * n - 0.5 * k * n1^2 + v0
speedSPS = ((this->accelerationRate * n1 + this->initialAcceleration) * stepsCompleted) - (0.5f * this->accelerationRate * pow(n1, 2)) + this->initialSpeedSPS;
} else { // (stepsCompleted >= n2)
// Deceleration
// a(n) = -k * n + k * n2 + a_max
// v(n) = -0.5 * k * n^2 + (k * n1 + k * n2 + a0) * n - 0.5 * k * (n1^2 + n2^2) + v0
speedSPS = (-0.5f * this->accelerationRate * pow(stepsCompleted, 2))
+ (this->accelerationRate * n1 + this->accelerationRate * n2 + this->initialAcceleration) * stepsCompleted
- (0.5f * this->accelerationRate * (pow(n1, 2) + pow(n2, 2)))
+ this->initialSpeedSPS;
}
this->setSpeedSPS(speedSPS);
}
```