Compact Joint Actuator

TK-120

120 mm outer diameter. Built for distal joints where every gram and millimeter counts.

The TK-120 is a compact BLDC joint actuator with a 100:1 harmonic drive gearbox, 19-bit absolute magnetic encoder, and full FOC firmware pre-tuned from the factory. Wrist, elbow, and ankle joints. 18 Nm continuous torque at 0.64 kg.

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TK-120 compact joint actuator — 120 mm outer diameter, harmonic drive, BLDC motor
18 Nm Continuous Torque
54 Nm Peak Torque
28 Nm/kg Torque Density
0.64 kg Mass
400 Hz FOC Bandwidth
Datasheet

Full specification

Mechanical
Outer Diameter120 mm
Stack Length58 mm
Output Shaft OD22 mm
Mass0.64 kg
Gearbox TypeHarmonic drive flex-spline
Gear Ratio100:1
Continuous Torque (25°C)18 Nm
Peak Torque (3 s)54 Nm
Torque Density28 Nm/kg
Cogging Torque (RMS)0.08 Nm
BackdrivabilityYes — impedance-transparent at low speed
No-Load Speed (output)0.9 rev/s
IP RatingIP54
Operating Temperature-20°C to +70°C
Electrical
Nominal Supply Voltage48 V DC
Supply Voltage Range24–48 V DC
Continuous Current Draw4.2 A
Peak Current (3 s)12.6 A
Motor TypeBLDC, outrunner topology
Motor Pole Pairs7
Motor Resistance (phase–phase)0.42 Ω
Motor Inductance (phase–phase)74 µH
Kv (motor constant)120 rpm/V
Encoder & Control
Encoder TypeAbsolute magnetic, AS5048 series
Encoder Resolution19-bit (524,288 CPR)
MCUSTM32G474 (170 MHz Cortex-M4)
FOC Control Loop Rate400 Hz
PWM Switching Frequency40 kHz
Position Control Latency<2 ms
Control ModesPosition, velocity, torque, impedance
Bus InterfaceCANopen CiA 402
CAN Baud Rate1 Mbit/s
Firmware UpdateOTA via CAN bootloader
ROS 2 NodeIncluded (hardware_interface)
micro-ROS SupportYes — via micro-ROS agent
MoveIt 2 SRDFProvided in SDK package
Performance

Torque-speed characteristic

Measured at 48 V, 25°C ambient, natural convection cooling. Continuous duty region is below the thermal limit curve.

0 18 36 54 0.3 0.6 0.9 Torque (Nm) Speed (rev/s) Peak (3 s) Continuous 54 Nm @ 0.9 rev/s 18 Nm @ 0.6 rev/s

Torque–speed envelope for TK-120 at 48 V, 25°C. Peak region thermally limited to 3 s bursts. Continuous region measured at steady-state with natural convection.

Integration

First torque command in under 10 minutes

TK-120 ships pre-tuned. No BLDC commutation setup needed. Power on, connect CAN, send CiA 402 control word.

  1. 01

    Power supply connection

    Connect 24–48 V DC to the M8 4-pin power connector (pinout in datasheet §3.1). Recommended supply: 48 V, 10 A minimum for single actuator. Common ground with CAN bus required.

  2. 02

    CAN bus connection

    120 Ω termination resistor on bus. Default Node-ID 0x01 (configurable via SDO write to object 0x2000). Baud rate: 1 Mbit/s fixed. Use M12 5-pin CAN connector.

  3. 03

    NMT state machine — Operational

    Send NMT Start Node command (0x01 0x00) to transition from Pre-Operational to Operational. CiA 402 state machine follows: Switched On → Operation Enabled via controlword 0x0006 → 0x0007 → 0x000F.

  4. 04

    ROS 2 hardware interface (optional)

    Install the tendonkindle_ros2 package from the SDK. Launch file maps a single TK-120 to a joint_state_controller and joint_trajectory_controller. Node-ID configurable in YAML. micro-ROS agent alternative for embedded targets.

  5. 05

    First torque command

    In torque mode (mode of operation 0x04), write target torque to object 0x6071. Range ±18 Nm continuous. Torque feedback available via TPDO1 at 1 ms period. Impedance mode available via firmware extension API.

Quickstart Guide ROS 2 Integration CANopen Reference
Dimensions

Dimensional drawing

All dimensions in millimeters. CAD files (STEP + URDF) available in the SDK package.

∅120 80 PCD 58 L TK-120 OD: 120 mm L: 58 mm Shaft: ∅22 mm M: 0.64 kg 8× M4 bolt circle

Schematic only. Download STEP file for mechanical design clearance. URDF with collision mesh in SDK package.

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