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Week 19: Project Development

This page tracks where my final project, the Robotic Gripper, stands right now. I've tried to be clear about what is done, what is being tested, and what is still only planned.

What does it do?

My final project is a robotic gripper that opens and closes a set of gripping fingers to pick up and hold suitable objects. A gear-based mechanism transfers movement from a servo motor to the finger linkages, so the fingers move towards or away from each other together. A microcontroller sends the control signal to the servo.

The intended sequence is:

  1. The gripper starts in an open position.
  2. The microcontroller commands the servo to move.
  3. The servo drives the gears and linkages.
  4. The fingers close and hold the object.
  5. The servo reverses to open the fingers and release it.

At this stage, the servo and microcontroller are being tested on their own. The full gripper still has to be assembled, driven by the servo, and tested with real objects.

Who's done what beforehand?

Robotic grippers are widely used in industrial automation, research labs, and educational robotics. Existing designs include parallel-jaw grippers, multi-finger grippers, gear-driven mechanisms, and servo-operated linkages. Open-source grippers and educational robot-arm projects were useful references for finger geometry, gear arrangements, and servo control.

I'm not trying to invent a new category of gripper. My focus is on developing my own implementation and understanding how its mechanical and electronic parts behave together.

What did I design?

  • The gripper structure and base that support the mechanism.
  • The gear arrangement that transfers motion to the fingers.
  • The gripping fingers, linkages, and pivots.
  • Mounting features for the servo, designed so it can be removed or replaced.
  • The circuit and PCB layout for the control system (in progress).
  • The servo-control code.

What sources did I use?

  • Existing robotic gripper designs, for finger geometry and mechanisms.
  • MG90S servo datasheet: voltage, torque, range of movement, current draw.
  • Seeed Studio XIAO RP2040 documentation: pinout, programming, servo control.
  • PCB and electronics references for circuit design and board fabrication.
  • Fab Academy documentation for fabrication, machining, PCB milling, and electronics workflows.

What materials and components are used?

Component / material Role Source Est. cost (₹) Status
3D-printed parts (PLA) Gripper body, fingers, supports Fab Lab 150–300 Fabricated / being refined
Gears Transfer motion to the fingers 3D-printed or bought 0–200 Fit and movement need validation
Shafts, pivots, fasteners Support the moving parts Local hardware store 100–250 To be finalised with the assembly
MG90S servo motor Drives the gripping movement Robu.in / ElectronicsComp 200–300 Standalone testing; suitability for the load not yet verified
Seeed Studio XIAO RP2040 Microcontroller for servo control Robu.in / Seeed Studio 450–650 In use for standalone testing
PCB and electronic components Control-system integration Fab Lab inventory 150–400 Design in progress
Wiring and connectors Electrical connections Fab Lab inventory / Robu.in 100–200 Being checked during testing
Regulated power supply Powers the servo Robu.in / local electronics shop 200–400 To be matched to the servo's requirements

Costs are estimates based on typical Indian prices (≈ ₹1,350–2,700 in total), not actual receipts. I'll replace them with real costs as I confirm them, and keep this table updated if any component changes after testing.

What parts and systems were made?

Mechanical system

  • Gripper base and support structure
  • Gear mechanism
  • Fingers and linkages
  • Servo mount

Electronic system

  • XIAO RP2040 and MG90S servo connections
  • Power supply arrangement (the servo is not powered from the XIAO's 3.3 V pin)
  • Custom PCB (in progress)

Software

  • Servo test code that moves between an open and a closed angle in small steps

What processes were used?

  • 3D modelling (Fusion 360): part and assembly models, checking clearances and fit.
  • 3D printing: fast iterations of the fingers, gears, supports, and mounts.
  • CNC machining: explored for mechanical parts where it suits the geometry.
  • Lathe machining: explored for rotational parts; see Wildcard Week.
  • PCB design (EasyEDA) and milling: for the control board.
  • Soldering and wiring: assembling and connecting the electronics.
  • Embedded programming: servo control on the XIAO RP2040.
  • Mechanical assembly and testing: checking alignment, friction, and movement.

What questions are being answered?

  • Does the gear mechanism move freely by hand, without binding?
  • Can the MG90S move the mechanism under load, or does it need a different actuator or gear ratio?
  • How can friction and misalignment be reduced?
  • Is the power supply enough for reliable servo operation?
  • Can the gripper repeatedly pick up, hold, and release objects without slipping?
  • How should the PCB and wiring be integrated into the structure?

These questions are still open. I'll update this section with actual results as I test.

What's working so far?

  • The mechanical concept and CAD models show how the gears, fingers, and mount fit together.
  • Fabricating physical parts has shown me where fit and alignment need more attention.
  • I've started testing the MG90S with the XIAO RP2040 on its own, to separate control problems from mechanical ones.

What isn't working yet?

  • Getting smooth movement despite the resistance in the gear mechanism.
  • Component alignment and fit still need checking against the CAD model.
  • It's not yet confirmed whether the MG90S has enough torque for the mechanism.
  • The PCB and full electronics integration are not finished.

How will it be evaluated?

I'll test in stages, so I can tell where any problem comes from:

  1. Mechanical check: move the mechanism by hand and look for binding, interference, and backlash.
  2. Standalone servo test: wiring, control pin, supply voltage, and a safe angle range.
  3. Servo + mechanism: start with a small range and watch for stalling, noise, or heating.
  4. Electronics integration: test the PCB on its own before connecting it to the gripper.
  5. Gripping test: objects of different sizes and shapes, recording what is picked up, held, and released, and why it fails when it does.
  6. Refinement: update the CAD, fabrication, actuator, or code based on the results.

What are the implications?

The gripper is a learning platform for robotic gripping, mechanical motion, and actuator control, and for combining fabricated parts with electronics. It could later be developed for educational robotics, small-scale object handling, or prototype automation. These are possibilities, not validated uses.

Possible future additions:

  • Object detection (an ultrasonic sensor was considered earlier but is not part of the current setup).
  • Force feedback.
  • Remote or wireless control.