Planar Elbow Manipulator — Design & Control
A 2-DoF planar elbow manipulator that uniquely met every mechanical requirement in ME408, integrating robust CAD, power electronics, and dual-loop control for precise trajectory tracking.
1 · Overview & Motivation
This solo ME408 project (Sabancı University) produced the only design in a class of 20+ that satisfied all structural, weight, and accuracy specs.
The goals were:
- Light-yet-strong mechanics — optimized with FEA
- Clean power delivery — custom buck-boost converter
- High-precision motion — gravity-compensated PI/PID dual-loop control
| Metric | Target / Result |
|---|---|
| Safety factor | > 2 (FEA) |
| Mass reduction | 18 % vs initial |
| Tracking error | ≤ 0.35 ° RMS @ 60 °/s |
| Loop latency | 2.4 ms @ 1 kHz |
2 · Mechanical Design
- CAD in SOLIDWORKS with topology-inspired link geometry
- Static & dynamic FEA → safety factor > 2 while trimming 18 % mass
- Modular joints for quick bearing replacement and encoder mounting
3 · Power Electronics
- Buck-boost converter designed in LTspice
- 7 % voltage ripple, < 5 % inductor current ripple at 1 A load
- Integrated Hall shunt for inner-loop current sensing
4 · Control Architecture
| Loop | Controller | Inputs | Outputs |
|---|---|---|---|
| Inner | PI | Motor current, Vin | PWM duty cycle |
| Outer | PID + g-comp | Joint angles, desired θ | Motor current set |
- Trajectories generated from inverse kinematics; simulated in MATLAB/Simulink
- Achieved ≤ 0.35 ° RMS tracking error on a 60 °/s sinusoid
5 · System Integration & Validation
All subsystems were co-simulated:
- Mechanics → SOLIDWORKS Motion
- Electronics → LTspice transient + Bode analyses
- Control → Simulink real-time plant-in-the-loop
CAD renders and closed-form workspace analysis.
Key FEA results confirming deformation < 0.12 mm and stress well below yield.
Completed for ME408 — Mechatronic System Design (Fall 2024).