PROJECT STAGES
When deciding the right way to start a project using the SG3Q contact-less strain gauge-based torque and angle sensing technology, it makes sense to consider what level of testing you need at the given stage of the project and the maturity level of the project. The below listed “test levels” or “testing stages” indicate what we typically see. Your desired outcome may be different – please get in touch to discuss your needs for torque, angle, and cadence sensor solutions.
If you just want to understand the benefit a real strain gauge-based torque sensor offers, read through the white paper where we compare magnetostrictive to strain gauge-based torque sensors.
Testing stage 1: Bench testing to validate the technology
When all you need is an on-the-bench test of the SG3Q technology as a first step in evaluating the SG3Q technology, the SG210 solution presented below is the best way. This allows convenient bench testing of torque/angle/cadence/technology/airgap/oil and grease compatibility/etc.
Testing stage 2A: Motor controller integration
One of the obvious next steps in a typical e-bike development project would be integrating the sensor with the motor controller. For other types of projects, this could be the interface to some other embedded system. This test is possible at the desk level in parallel with other mechanical tests as described under Level 2B.
If the system receiving the sensor data is flexible, this interface can be the standard offered in the SG210 sensor and can be tested using that product.
On the other hand, if you need a custom interface on the sensor side, one of two options could make sense:
- With the SG30 sensor module set, we can make a custom interface/protocol within what is possible with that module (serial data interface)
- With a full custom SG3Q sensor system design, many more interfaces are available and can be tested on the desk (serial, I2C, SPI, analog, Quadrature, CAN, etc.)
Making sure custom protocols are adjusted and aligned between the sensor and motor controller (or another embedded system) is essential before the next levels and should often happen in parallel with mechanical integration tests.
Testing stage 2B: Mechanical motor integration
For testing the sensor works well and fits inside an unpowered motor it makes sense to use an SG30 or a full custom SG3Q sensor. In any case, this requires full mechanical integration into a motor/gear/other system. Typically this comprises the following steps:
- You design the metal part in the torque path including the torque sensing element. For this, we run the “torque sensing design workshop” with you to help you do it right. It is not difficult to do, but it is super essential to get right. We have a lot of experience in this and will help as much as we can.
- You manufacture the metal parts while we make the electronics
- We provide the SG bonding service so we can assemble and test the complete sensor prototypes here.
For testing torque response, we need to establish a good test setup. It is essential to have the same test setup on both sides (or physically meet in Copenhagen to perform the testing together). We have the basic test machine CalStand for this and can tell you how to make an adaptor for most mechanical systems – or we can use a copy of your test setup.
Testing stage 3: Live motor integration
As for any complex electromechanical system, it is important to test the total system integration with the close involvement of key component suppliers. As some motors and motor wiring have very high currents really close to the sensor, the SG3Q technology has been designed to be very rugged. This includes adjustable filtering if needed in cases where the integration with the motor and motor controller makes this important.
This level is also where EMC/EMI and other regulatory tests can often be done – or at least screened for to make sure the project sails through the formal testing later.
Testing stage 4: Integration on a demo bike
We verify the integrity of the sensor system on the bike with all that is needed for this. One of the key things that happens on a bike, which is different on the test bench, is other forces that are not pure torque. We address this already at the bench test level as our typical test system is applying a combination of bending forces and torque.
On the bike, things are different and test riding a demo bike is typically where the entire system integration is judged. For this reason, we work to ensure the success of this crucial step with data logging sensor data in parallel with the other instrumentation available.
PRODUCTS AND SERVICES
The below products and services are designed to make this process simple and efficient.
SG210 Torque/angle sensor reference design
A reference torque sensor as proof-of-concept/evaluation/technology demonstration. We offer a complete sensor to demonstrate the technology and get a quick head-start in any torque sensor project. The two key issues for most e-bike applications are a delay in cadence detection and an offset/zero-point stability in the torque sensor.
- The SG210 measures cadence based on inductive absolute angle measurements with 1 deg resolution. This results in an ultrafast cadence response without the use of permanent magnets.
- Torque offset stability performance is market-leading due to the strain gauge technology used. Learn more about what makes our strain gauge-based technology so much better than magnetostrictive sensors for torque measurements on e-bikes.
Other types of applications have different requirements. If the requirements are somewhat similar, this type of sensor can be a great match for many other applications.
SG30 Torque/angle sensor module set
This sensor module set is ready for integration in any gear/BB/mid-drive/hub-drive/industrial design. This is also the module that we use in the SG210 reference design. This is designed for use on tube-shaped torque-metal parts (shaft, axle, hollow shaft, etc.).
To accompany this, we combine this with:
- The torque-metal-design workshop teaches how to design the bending metal part where the strain gauge bonds. This is where most of the performance of the complete sensor system is defined. Often the most critical part. Not difficult to do, but needs to be done right.
- Strain gauge bonding and testing service. We perform complete assembly and create a test report for the first complete sensor prototypes.
The specific design may be able to use SG30 if the physical shape and size work for the application and the interface is acceptable, or for early-stage “mule” type proof-of-concept projects. In case this is not a good fit, the core technology can be customized to fit as described below.
SG3Q Full custom torque sensor project
This is a complete custom sensor design where we create 100% custom torque and cadence sensor solutions to fit exactly into any mechanical design. The usual procedure typically includes four phases, during which we take the project from inception to production.
We agree on a specification and provide prototypes in stages that align with the project phases. For e-bike projects, the stages typically proceed as follows:
1) Proof of concept (maybe using SG210 or SG30)
2) First revision of 100% custom sensor fitting customer-designed metal (typically 3-5 units)
- Torque metal design workshop where we help you understand and design the metal part when installing strain gauges.
- Agree on customized parameters based on the specifications of the SG30 we agree on the changes needed.
- You manufacture mechanical parts and we customize the electronics.
- We assemble and provide the strain gauge bonding service for the prototypes.
- Bench-level testing to verify performance with the agreed test setup.
- Integration with the motor controller to verify the customized electrical interface.
- Integration with live motor to verify optimal performance and no interference between motor and sensor.
- Integration on a running bike to get ready for a live demo of the full system integration.
3) Production-ready revision with learnings from the first revision. Used for final validation before kicking off series production. Typically 10-50 units.
4) Pilot and production ramp-up, where we follow the project till the end. Can be based on production by Sensitivus (typically lower volumes) and by the customer (license model).
SENSITIVUS GAUGE