Mechanisms · Mechatronics · CAD · Control

Five-BarMechatronic System

A two-degree-of-freedom five-bar robotic manipulator developed through mechanical design, CAD, kinematic modelling, physical prototyping, electronics integration and simulation-based control.

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Concept Development

The early concept stage established the five-bar linkage arrangement, motor positions, base geometry and end-effector location. The design was refined around a compact base-mounted layout so the actuators could remain fixed while the linkage generated planar two-degree-of-freedom motion.

01Base-mounted motors
02Reduced moving inertia
03Symmetric planar motion
04Motor and wiring clearance
05End-effector development

Initial robot sketches exploring motor placement and linkage geometry — Initial sketches

Final annotated concept sketch of the five-bar mechanism — Concept drawing

CAD & Mechanical Design

The CAD model developed the five-bar concept into a complete mechanical assembly, allowing the linkage geometry, actuator placement, bearings, base structure and end-effector region to be coordinated before manufacture.

Design trade-offs included balancing symmetry and compactness against wiring access, stiffness, backlash and manufacturing tolerances. The final concept used base-mounted actuation, bearing-supported joints and lightweight printable structural components.

Exploded CAD assembly showing the robot's mechanical components — Assembly architecture

Engineering drawing of the final five-bar mechatronic system — General assembly drawing

Five-bar kinematic model showing joints A, B, C, D and end-effector point P

Kinematic Modelling

The robot was modelled as a planar five-bar closed-chain mechanism with two grounded revolute joints and one common end-effector point. Forward kinematics were used to calculate the end-effector position from the two actuated joint angles, while inverse kinematics calculated the required joint angles for a desired Cartesian position.

2 DOFFive-bar closed chainForward + inverse kinematics

Physical Build & Electronics

The physical prototype combined the five-bar linkage with two base-mounted EMG30 geared motors, an Arduino Mega 2560, L298N motor driver, encoder-capable actuation and a fabricated mechanical structure.

Assembly highlighted the practical influence of joint clearance, shaft alignment, screw length, linkage accuracy, backlash, wiring complexity and structural stiffness.

Physical five-bar robot prototype with wooden links, motors and electronics — Fabricated five-bar prototype

Arduino Mega and L298N wiring diagram for the robot — Electronics and encoder wiring

Arduino Mega 2560: Control and I/O platform
2 × EMG30 Motors: Geared DC motors with encoders
L298N Driver: Bidirectional motor interface
Encoder Feedback: Intended for future hardware closed-loop control

Simulation & Control

Joint position control was investigated in MATLAB/Simulink using two independent PID loops acting on simulated motor-plant models. The control architecture was then connected to the inverse- and forward-kinematic models to evaluate coordinated Cartesian point regulation.

The simulated end effector converged to the desired Cartesian target, although the transient path was curved because the two joints had different rise, overshoot and settling characteristics.

Coordinated Cartesian tracking plots from Simulink

Desired Cartesian pointInverse kinematicsTwo simulated PID joint modelsForward kinematicsReconstructed end-effector position

The end effector converged to the desired point, but the differing joint transients produced temporary Cartesian path deviation.

Final Outcome

The robot was developed as a two-degree-of-freedom five-bar robotic manipulator, progressing from concept through CAD, kinematic modelling, physical assembly, electronics integration and simulation-based control. The project demonstrated the relationship between mathematical modelling and real mechanical behaviour, while highlighting the importance of stiffness, joint accuracy, backlash reduction, wiring quality and coordinated joint response.

Future development would focus on physical encoder-based PID implementation, reduced mechanical backlash and full Cartesian trajectory tracking.