High-Torque Joint Actuator

TK-240

240 mm outer diameter. The torque-density optimum for hip, knee, and shoulder joints in humanoid platforms.

The TK-240 reaches 42 Nm/kg peak torque density — the number robotics OEMs are trying to close. 42 Nm continuous, 120:1 harmonic drive, EtherCAT CoE and CANopen on the same board. One actuator that handles the critical mid-body joint positions.

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TK-240 high-torque joint actuator — 240 mm outer diameter, EtherCAT and CANopen dual bus
42 Nm Continuous Torque
126 Nm Peak Torque
42 Nm/kg Torque Density
1.01 kg Mass
Dual Bus EtherCAT + CANopen
Datasheet

Full specification

Mechanical
Outer Diameter240 mm
Stack Length72 mm
Output Shaft OD38 mm
Mass1.01 kg
Gearbox TypeHarmonic drive flex-spline
Gear Ratio120:1
Continuous Torque (25°C)42 Nm
Peak Torque (3 s)126 Nm
Torque Density42 Nm/kg
Cogging Torque (RMS)0.12 Nm
BackdrivabilityYes — impedance-transparent
No-Load Speed (output)0.75 rev/s
IP RatingIP54
Operating Temperature-20°C to +70°C
Electrical
Nominal Supply Voltage48 V DC
Supply Voltage Range48 V DC
Continuous Current Draw9.8 A
Peak Current (3 s)29.4 A
Motor TypeBLDC, outrunner topology
Motor Pole Pairs10
Motor Resistance (phase–phase)0.18 Ω
Motor Inductance (phase–phase)42 µH
Kv (motor constant)85 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
Primary BusEtherCAT CoE (100BASE-TX)
Secondary BusCANopen CiA 402 (1 Mbit/s)
Firmware UpdateOTA via EtherCAT FoE or CAN bootloader
ROS 2 NodeIncluded (hardware_interface)
micro-ROS SupportYes — via micro-ROS agent
MoveIt 2 SRDFProvided in SDK package
Characterization

Dyno test results — thermal derating

Continuous torque limit as a function of ambient temperature. Measured on dynamometer with forced-air cooling off (natural convection).

0 14 28 42 0°C 25°C 50°C 70°C Cont. Torque (Nm) Ambient Temperature 43 Nm 42 Nm 36 Nm 28 Nm Rated: 42 Nm @ 25°C

Continuous torque output at each ambient temperature, natural convection, 30-minute steady-state. Derate by ~16% at 50°C, ~33% at 70°C. Full derating table in datasheet §4.2.

EtherCAT Bus

EtherCAT CoE daisy-chain topology

TK-240 is the first Tendonkindle actuator to support EtherCAT as primary bus — suited for applications where deterministic cycle time matters at the joint level.

EtherCAT Master (PC) TK-240 #1 Node 0x01 TK-240 #2 Node 0x02 TK-240 #N Node 0x0N 100BASE-TX CAT5e / CAT6 — up to 16 actuators per chain
  • Cycle time250 µs minimum (EtherCAT DC sync)
  • Max daisy-chain length16 actuators per chain
  • Cable typeCAT5e or CAT6 shielded
  • ESI fileProvided in SDK — load into TwinCAT 3 or SOEM
  • CoE PDO mappingPosition, velocity, torque, status in TPDO1
  • Distributed clocksSupported — <1 µs synchronization across joints
EtherCAT Setup Guide ROS 2 Integration Firmware API Reference

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