Our culture at MagCanica has always been focused on the accuracy of the sensor when installed in the vehicle and when used under typical operating conditions. When discussing errors with our customers, we prefer not to focus on ‘Accuracy Class’ or designations that classify errors separately such as temperature, those associated with non-torsional loads, and only test by considering the application of carefully controlled loads. While these classifications do have a place, when they are the key focus and objective, in our opinion they mask just how accurate the sensor will be when installed in your vehicle.
Our culture at MagCanica has always been focused on the accuracy of the sensor when installed in the vehicle and when used under typical operating conditions. When discussing errors with our customers, we prefer not to focus on ‘Accuracy Class’ or designations that classify errors individually (such as temperature, those associated with non-torsional loads, etc.) or error designations that only test by considering the application of carefully controlled loads, which are not representative of in-vehicle load profiles. While these classifications do have a place, when they are the key focus and objective, in our opinion they mask just how accurate the sensor will be when installed in-vehicle in a demanding environment, as opposed to under controlled laboratory conditions.
The MagCanica UHA ultra high accuracy driveshaft torque system has been developed and optimized over many years, with the goal of achieving ‘laboratory grade’ accuracy while operating in-vehicle, not under controlled laboratory conditions. Our goal, now proven, has been to develop a sensor that has better than 0.25% accuracy of reading (above a minimum threshold as the % reading when close to 0Nm becomes unrealistic) when operating in its final installation environment on a vehicle. The accuracy should be evaluated with realistic loading scenarios (e.g. lap simulations or flight simulated loads) as well as conceived worst-case conditions), over the full-range of operating temperatures, when exposed to all possible vibrations, and with standard acquisition equipment suitable for use in a vehicle.
To meet these goals, the UHA sensor was designed to minimize each potential source of error:
- Errors associated with variations in the relative position between the sensor and shaft are eliminated by riding on the shaft.
- Errors associated with external magnetic fields by using highly effective shielding and a ‘keep out zone’ between the sensor and nearby ferromagnetic objects.
- Temperature and hysteresis errors through extensive testing of each sensor, and the use of sophisticated compensation models that run real-time on the integrated DSP in combination with proprietary calibration characterization algorithms and associated digital infrastructure.
- Unlike other technologies, bending stresses are fundamentally rejected and do not interfere with the measurement of torque.
- Signal transmission errors are eliminated by using a digital (e.g. CAN or CAN-FD) output
Figure 1 First generation
high accuracy drive-shaft sensor
In the case of MagCanica’s Ultra High Accuracy (UHA) driveshaft torque sensor system, while much of our efforts to design and test the system did use controlled tests to quantify the errors and improve the system, extensive dynamometer and in vehicle testing have also been critical to its development in particular in regards to evaluating reliability. The first generation UHA sensor (was designed in 2016 and tested in 2017 through a combination of development within MagCanica and through the use of dynamometer and track tests. Internal developmental testing at MagCanica consisted of extensive development time on our static torque testing rigs used to apply torque and our speed testing rig to test the durability of the integrated bushings. Testing outside of MagCanica consisted of numerous dynamometer and in-vehicle tests.
Figure 2 Second generation
high accuracy drive-shaft sensor
The design was quickly iterated upon in order to optimize the package and improve reliability. This second generation design allowed the sensor to be radially installed onto the shaft, allowing the use of integrated tripods on the shafts if needed. Sealing was provided with a custom bushing and seal design. MagCanica’s latest generation of electronics was integrated. The weight was cut by ~100 grams. Both internal testing, as well as dynamometer and in-vehicle testing, confirmed the improvements, as we received excellent feedback in regards to both reliability and accuracy.
In addition to shorter-duration dyno and track tests, we were highly focused on ensuring excellent reliability even during the use over the course of a full 24-hour endurance race. As testing of this duration is not easy to come by, MagCanica partnered with a premier motorsport supplier, Pankl Racing Systems, to carry out a full 24-hour dynamic dyno test, applying full lap simulations which included driveshaft dynamics associated with suspension travel and representative temperatures. This testing was completed successfully without any reliability issues.
Since 2018, the development work on the UHA has continued, focused on further improving accuracy through complex modeling and signal correction algorithms carried out within the firmware. The MagCanica UHA driveshaft torque sensor system has now become the industry standard for in-vehicle torque instrumentation, with a fleet of over 1,000 UHA systems typically running in the field at any given time.
Design and production of the UHA sensor and dynamic dyno testing
Figure 3 Image of two UHA sensors installed
Figure 4 Image of the two UHA sensors
while being monitored with a thermal camera.