Legs and Testbeds
This page covers the individual leg modules and test platforms used for development, validation, and performance evaluation of the Open Robot Actuator Hardware.Leg Modules
2DOF Leg v2
2DOF Leg v2
Two-degree-of-freedom leg with Hip FE and Knee jointsApplications:
- Quadruped Solo8 v2
- Leg Test Stand v2
- Simplified locomotion research
- Hip Flexion/Extension joint
- Knee joint
- Total weight: ~200g (depending on configuration)
Hip Module Shell
- Base: 27g
- Cover: 15g
Upper Leg Module Shell
- Base: 27g
- Cover: 15g
- Lower Leg v2: 20g (FDM printer with “sparse double dense” setting)
- Lower Leg v3: 20g (solid part, alternative to v2)
3DOF Leg v1
3DOF Leg v1
Three-degree-of-freedom leg used in Solo12 quadrupedWeight: 485g per legJoints:
- Hip Abduction/Adduction (AA)
- Hip Flexion/Extension (FE)
- Knee
- Quadruped Solo12
- FingerEdu modules
- NYU Finger
- Hip AA Module Shell Base: 21g
- Hip AA Module Shell Cover: 16g
- Hip FE Module Shell Base: 25g (standard) or 26g (Alt A)
- Hip FE Module Shell Cover: 16g
- Upper Leg Module Shell Base: 27g
- Upper Leg Module Shell Cover: 15g
- Lower Leg v2 or v3: 20g
Hip FE Alternative Base Shell
Hip FE Alternative Base Shell
An alternative version of the Hip FE Base shell (Alt A) is available to simplify wire routing. This design improvement was contributed by Pau Martinez.See GitHub Issue #38 for details.
Joint Rotation Limiters
Joint Rotation Limiters
Optional rotation limiters can be installed to prevent multiple rotations and wire winding:
- Single Stopper: Limits upper leg rotation (14g)
- Double Stopper: Limits both upper and lower leg rotation
- Uses silicone tube sections to soften impacts
- Compatible with foot-switch configurations
| Component | Quantity | Notes |
|---|---|---|
| Core Components | 3 | Actuator module cores |
| 3D Printed Shell Parts | 1 set | See list above |
| Rubber Foot | 1 | Bicycle tire segment (75mm x 7mm) |
| M3 Fasteners | Various | Different lengths for connections |
| M2.5 Fasteners | 27 | Socket head cap screws |
| Helical Inserts M2.5x3.75 | 27 | 1.5xD |
| Washer M3 | 2 | Stainless steel |
Test Platforms
Leg Test Stand v2
Leg Test Stand v2
Advanced testing platform for 2DOF leg evaluation with external sensorsKey Features:
- Linear guided vertical DOF (85cm range)
- 6-axis force-torque sensor
- Height sensor (string potentiometer)
- Optional pull-up motor for automated reset
- Vertical range: 85cm
- Pull-force height sensor: ~2N
- Carriage weight (with electronics and leg): 713g
- Power: 24V, Ethernet communication
Force-Torque Sensor
ATI Mini-40-E
- 6-axis measurement
- SI-40-2 calibration
- NetBA interface box required
- Ethernet communication at 1kHz
Height Sensor
Waycon LX-PA-40
- String potentiometer
- 1000mm measurement range
- Analog output
- Continuous position tracking
- Master Board v2: 19g
- Micro Driver Board v2: 13g (1 board for 2 motors)
- Total electronics stack: 45g
Linear Guide System
- Linear ball bearings: 4x KB-1 14mm
- Precision stainless steel rods: 2x 14h6 x 1000mm
- Linear bearing covers (3D printed)
Frame Structure
- Item aluminum profiles (Size 8)
- Segments: 120cm, 70cm, 50cm, 30cm
- 4x angle brackets 40mm
- 5x end caps
| Component | Printing Method | Notes |
|---|---|---|
| Carriage | FDM or SLS | Main moving platform |
| Master Board Support | FDM or SLS | Electronics mounting |
| Spacer Micro Driver Stack | SLA/Polyjet/Multijet | 8 pieces |
| Linear Bearing Cover | FDM or SLS | 4 pieces |
| Adjustment Sleeve | SLA/Polyjet/Multijet | 4 pieces |
| Linear Motion Rod Attachment | FDM or SLS | 2 pieces |
| String Pot & Pullup Motor Mount | FDM or SLS | Sensor mounting |
| ATI Sensor Top Plate | FDM or SLS | FT sensor mount |
| ATI Sensor Bottom Plate | FDM or SLS | FT sensor mount |
| Stopper Attachment | FDM or SLS | 2 pieces |
| Stopper Wing | FDM or SLS | 1 piece |
- Enables machine learning experiments
- Automated return to initial position
- Custom motor driver electronics
- Pulley system with custom 3D printed pulley
- Steel pins: 2x 5mm x 28mm
- Carbon-fiber tube: O.D. 6mm, I.D. 4mm, Length 30cm (wire management)
- T-slot nuts M5: 7 pieces
Applications and Use Cases
Development and Testing
Individual Leg Characterization
Individual Leg Characterization
The test stand allows precise measurement of individual leg performance:
- Force-torque profiles during motion
- Vertical height tracking
- Hopping and landing dynamics
- Controller validation
Machine Learning Experiments
Machine Learning Experiments
The automated reset capability enables:
- Reinforcement learning trials
- Hopping height optimization
- Energy efficiency studies
- Repeated experiment automation
Component Validation
Component Validation
Test stands verify:
- Actuator module performance
- Electronics integration
- Mechanical assembly quality
- Software control loops
Modular Design Benefits
The leg modules share core components across platforms: Shared Components:- All actuator modules use identical internal components
- Same core components in Actuator Module v1 and v1.1
- Reduces spare parts inventory
- Simplifies maintenance procedures
- Enables easy upgrades
| Leg Type | Used In | DOF | Weight |
|---|---|---|---|
| 2DOF Leg v2 | Solo8 v2, Test Stand v2 | 2 | ~200g |
| 3DOF Leg v1 | Solo12, FingerEdu, NYU Finger | 3 | 485g |
| Biped Leg 3DOF | Biped Bolt | 3 | 540g |
Assembly Resources
2DOF Leg Assembly
Complete build guide for 2DOF leg
3DOF Leg Assembly
Complete build guide for 3DOF leg
Test Stand Setup
Leg test stand v2 assembly guide
Actuator Modules
Core actuator module documentation
Lower Leg Options
Two lower leg versions are available for both 2DOF and 3DOF legs: Lower Leg v2:- Weight: 20g
- Printing method: FDM with “sparse double dense” setting
- Optimized for strength-to-weight ratio
- Requires specific slicer settings
- Weight: 20g
- Printing method: Solid part (FDM or SLS)
- Simpler to manufacture
- Alternative to v2 with same performance
NYU Finger v1
NYU Finger v1
Three-degree-of-freedom robotic finger using 3DOF leg componentsApplications:
- Dexterous manipulation research
- Writing and drawing tasks
- Precision positioning experiments
- Uses same actuator modules as 3DOF leg
- 3 DOF configuration
- External power and Ethernet communication
- Pen holder attachment available
- Master Board with adapter plate: 19g
- 2x Micro Driver Boards: 13g each
- Total electronics weight: 45g
- Modular design sharing components with 3DOF leg
- Interchangeable finger adapter and pen holder
- Compact footprint for tabletop experiments
- Compatible with existing control software
Dual Motor Testbed v1
Dual Motor Testbed v1
Simplest mechanical setup for learning brushless motor torque controlPurpose:
- Introduction to field-oriented control (FOC)
- Motor characterization and testing
- Control algorithm development
- Educational platform
- 2x T-Motor Antigravity 4004 motors
- 2x Broadcom AEDT-9810 encoders
- Custom motor shaft (stainless steel)
- 3D printed mounting structure
- No complex mechanical transmission
- Direct motor shaft encoder mounting
- Table-clampable design
- Works with TI evaluation boards or Micro Driver
- Torque control at all speeds including stall
- Getting started with motor control
- Testing motor driver electronics
- Control algorithm validation
- Educational demonstrations
Bill of Materials - Test Stand v2
| Component | Quantity | Notes |
|---|---|---|
| 2DOF Leg v2 | 1 | Custom assembly |
| Master Board | 1 | Custom electronics |
| Micro Driver Board | 1 | Custom electronics |
| String Potentiometer Waycon LX-PA-40 | 1 | 1000mm range |
| ATI Mini-40-E FT Sensor | 1 | With SI-40-2 calibration |
| Linear Ball Bearings KB-1 14mm | 4 | Stainless steel |
| Linear Motion Rods 14h6 x 1000mm | 2 | Precision ground |
| Aluminum Profiles Size 8 | 4 segments | Lengths: 120/70/50/30cm |
| Angle Brackets | 4 | Item 0.0.411.15 |
| End Caps | 5 | Item 0.0.026.01 |
| 3D Printed Parts | Various | See list above |
| Fasteners | Various | M2, M2.5, M3 stainless steel |
| Steel Pins 5mm x 28mm | 2 | For bearing alignment |
| Carbon Fiber Tube 6mm | 1 | 30cm length |
Related Resources
Actuator Module Core
Core components used in all legs
Electronics Wiring
Wiring guides and schematics
3D Printing Guide
Settings and materials for parts
Test Stand CAD
Interactive 3D CAD viewer