Motor Specifications

Detailed specifications for Encos motors used in Asimov bipedal legs

Overview

Asimov uses high-performance actuators from Encos, a manufacturer specializing in compact, high-torque servo motors for robotics applications. Each joint type uses a specific motor model optimized for its torque and speed requirements.

All motors are off-the-shelf components, ensuring availability and reducing custom manufacturing requirements.

Motor Models by Joint Type

Each joint in the Asimov leg uses a specific Encos motor model selected for optimal performance:

| Joint Type | Motor Model | Peak Torque | Application | |----------------|----------------------|-------------|------------------------------------|| | Hip Pitch | EC-A6416-P2-25 | 120 Nm | Hip flexion/extension | | Hip Roll | EC-A5013-H17-100 | 90 Nm | Hip abduction/adduction | | Hip Yaw | EC-A3814-H14-107 | 60 Nm | Hip internal/external rotation | | Knee Pitch | EC-A4315-P2-36 | 75 Nm | Knee flexion/extension | | Ankle A | EC-A4310-P2-36 | 36 Nm | Ankle dorsi/plantarflexion | | Ankle B | EC-A4310-P2-36 | 36 Nm | Ankle inversion/eversion |

Detailed Motor Specifications

Hip Pitch Motor: EC-A6416-P2-25

The hip pitch joint requires the highest torque in the leg system to support the robot’s weight and enable rapid leg swing during walking.

Key Specifications

• Peak Torque: 120 Nm
• Application: Hip flexion/extension movements
• Mounting: Direct drive configuration
• Range of Motion: -120° to +57° (left), -57° to +120° (right)
• Use Case: Primary actuator for forward/backward leg swing during gait

Hip Roll Motor: EC-A5013-H17-100

The hip roll motor enables lateral leg movements critical for balance and side-stepping maneuvers.

Key Specifications

• Peak Torque: 90 Nm
• Application: Hip abduction/adduction movements
• Range of Motion: -45° to +45° (both legs)
• Use Case: Lateral stability and side-stepping during locomotion

Hip Yaw Motor: EC-A3814-H14-107

The hip yaw motor provides rotational control around the vertical axis of the leg.

Key Specifications

• Peak Torque: 60 Nm
• Application: Hip internal/external rotation
• Range of Motion: -45° to +45° (both legs)
• Use Case: Turning maneuvers and orientation adjustments

Knee Pitch Motor: EC-A4315-P2-36

The knee actuator enables leg flexion and extension, crucial for shock absorption and push-off.

Key Specifications

• Peak Torque: 75 Nm
• Application: Knee flexion/extension
• Range of Motion: 0° to +86° (left), -86° to 0° (right)
• Use Case: Stance phase support, swing phase clearance, and shock absorption

Ankle Motors: EC-A4310-P2-36

Both ankle actuators use the same motor model, working together through the RSU mechanism to control ankle pitch and roll.

Key Specifications

• Peak Torque: 36 Nm (each motor)
• Application: Ankle dorsi/plantarflexion and inversion/eversion (coupled)
• Range of Motion: -70° to +70° (both A and B motors)
• Use Case: Ground contact control, balance adjustments, and terrain adaptation

The ankle motors work in a coupled configuration through the RSU mechanism. The actual ankle pitch and roll angles are derived from the combined positions of motors A and B. See the Ankle Mechanism page for details.

Motor Selection Rationale

1. Torque Requirements

   Each motor was selected to meet or exceed the peak torque requirements calculated from dynamic walking simulations and worst-case loading scenarios.

2. Size and Weight Constraints

   Encos motors provide excellent torque-to-weight ratios, minimizing the overall leg mass while maintaining required performance.

3. Thermal Performance

   All motors include integrated thermal management, allowing for sustained operation during continuous walking cycles.

4. Integration

   Standardized mounting interfaces simplify mechanical integration and enable field serviceability.

Sourcing Information

Primary Supplier

Encos Robotics

Manufacturer: Encos
Website: http://encos.cn
Product Line: High-performance servo actuators for humanoid robotics

Ordering Considerations

When ordering motors for Asimov:

• Verify the exact model numbers from the table above
• Order matched pairs for left/right symmetry when possible
• Consider ordering spare motors for critical joints (hip pitch, knee pitch)
• Lead times may vary; plan for 4-8 weeks for custom orders

Motor Control Requirements

Each Encos motor requires:

• Position control interface: CAN bus or RS-485 communication
• Power supply: 48V DC nominal (range 42-54V)
• Current capacity: Varies by motor, typically 10-30A peak per motor
• Encoder feedback: Integrated absolute encoders for position sensing

Performance Characteristics

High Torque Density

Encos motors provide industry-leading torque-to-weight ratios, essential for humanoid locomotion.

Fast Response

High-bandwidth servo control enables rapid adjustments during dynamic walking.

Robust Design

Sealed housings protect against dust and moisture in real-world operating environments.

Integrated Drivers

Built-in motor drivers simplify electrical integration and reduce wiring complexity.

Next Steps

Mechanical Design

Learn about the overall mechanical structure and joint specifications

Ankle Mechanism

Understand how the ankle motors work together in the RSU mechanism