ROBOTIC TENDONS / LINEAR ACTUATORS
Tendon tension sensing & actuator force control
Start with the force you need to observe: tendon pretension, distal cable force or axial actuator force. Then choose the sensing location, mechanical interface and independent acquisition channels together.
SENSOR LOCATION CHANGES THE MEASURAND
Separate transmitted tension from routing friction.
A tendon–sheath transmission introduces pose- and direction-dependent friction and hysteresis. Proximal tension therefore cannot simply be treated as the force delivered at the far end of every curved route.
For an idealized capstan-type contact, the limiting tension ratio is represented by T_high / T_low ≈ exp(μθ), with wrap angle θ in radians. Real sheath compliance, changing contact, pretension and reversals require system characterization; this expression is a screening model, not a controller calibration.
Published tendon–sheath force-balance model ↗Specify the small signal and the assembly peak separately.
Include minimum useful force increment, pretension, maximum working force and transient assembly loads. Cable stiffness and the mass of a moving sensor can bias a small-force reading.
Review a threaded S-frame, eyelet or clevis against the actual tendon route. Mechanical stops need a verified protection rating and clearance for the proposed geometry.
Configure MT-ILC-SUB interfaces →Give each required tendon force its own channel.
| Decision | Required input | Why it matters |
|---|---|---|
| Channel count | Independent forces, spare channels and shared timestamps | One summed signal cannot recover separate tendon tensions. |
| Per-channel sampling | Rate after multiplexing, filters and averaging | Converter headline rate may be shared across channels. |
| Data throughput | Channels × samples/s, plus framing and timestamps | Illustration: 16 × 1,000 Hz = 16,000 samples/s before protocol overhead; not a quoted hardware capability. |
| Delay and synchronization | Sensor/conditioner response, transport and controller period | Update rate and end-to-end latency are different quantities. |
| Output integration | SPI/UART, CAN-FD, USB or other required interface | Protocol, supply, grounding and software support require a matching integration definition. |
Keep actuator stroke and the load axis in the drawing.
For an electric cylinder, a male-to-female interface can place the force sensor between the pushrod and attachment without a separate gender adapter. Check shoulder spacing, usable engagement, jam nuts and cable bend radius.
Define off-axis exposure and any alignment joint. A force sensor measures the load through its structure; it does not correct an incorrectly constrained linkage.
Configure the actuator rod interface →Commission mechanics, then the signal, then the control loop.
- Check travel, alignment, attachment freedom and mechanical stops.
- Confirm wiring, excitation, zero, polarity and engineering-unit scaling.
- Record noise and drift with the actuator disabled and then energized.
- Apply known loads and evaluate motion across representative poses.
- Validate filters, transport timing and controller response as a complete system.
Application examples describe engineering review paths; medical or other regulated system use requires its own validation.
Resolve the fit, signal and calibration questions.
Where should the tendon tension sensor be installed?
Place it to observe the force relevant to the control objective. A proximal sensor includes the effects of a downstream frictional sheath; a distal location changes mass, packaging and cable-routing constraints. Validate the selected layout across representative poses.
Can several tendons share one bridge input?
A summed bridge signal does not preserve separate tendon forces. Independent tension feedback needs an independent measurement channel per required force, with synchronization and latency specified.
Does a higher sample rate guarantee a faster force loop?
No. Sensor mechanics, conditioner bandwidth, anti-alias filtering, transport, controller execution and actuator dynamics all contribute to response and stability.
ENGINEERING RFQ / SAMPLE REQUEST
Send the load case.
Define the interfaces.
Include both thread ends, working and peak force, available space and the signal your controller expects.
Company and university email domains are preferred. Prototype and research inquiries are welcome.
inquiry@inlineloadcell.com ↗