Taking Torque Measurement from the Lab to the Production Floor and Out into the Field
The primary challenge for off-highway vehicles is to work efficiently, whatever the terrain.
Rising fuel prices and the operators’ desire for lower costs have prompted vehicle manufacturers to design ever more economical vehicles with higher efficiency and reduced emissions. Many vehicles now automatically monitor and optimise effectiveness while the vehicle is being operated to ensure maximum efficiency. The combination of real-time force measurements with Internet-of-Things commmunication, plus ruggedised on-board computing with Artificial Intelligence software, paves the way for Autonomous Vehicles in Farming and Mining.
The OEM Sensors team at HBK plays a key role in these advances by providing the data that feeds the control loop. Since standard Sensors are seldome available in the size or format that Design Engineers require for a new vehicle, they turn to HBK for the design and custom sensors.
The purpose of a tractor is the same today as it was in the 19th century, when the first steam-powered machines were developed: to deliver high power, traction and torque at a controllable speed. Over time, the design has evolved and expanded into a wide range of off-highway vehicles that perform critical functions in a wide variety of industries. Whether they are used in agriculture or earth moving, in commercial or military applications, the primary challenge for these vehicles is to work efficiently, whatever the terrain.
To perform at their best, the wheels of these heavy, off-highway vehicles must stay in constant contact with the ground. And to do this, the power from the engine must be delivered consistently through the drivetrain and the gearboxes to all the wheels. For example, a tractor specifically designed to reduce wheel slip will combine an efficient engine and drivetrain system that sees very little power loss to the wheels, the power take-off (PTO) or the implement. Why go to all that effort? Because improvements in operational efficiency improve safety and reduce accidents; increase work rates and optimise profit for the operator.
Rising fuel prices and the operators’ desire for lower costs have prompted manufacturers to design ever more economical vehicles with higher efficiency. At the same time, governments around the world are setting stricter fuel efficiency standards for both on-highway and off-highway vehicles to reduce vehicle emissions. Attaining these goals delivers benefits for both the environment and vehicle operators. Since 2019, manufacturers of diesel-powered engines, transmissions, gearboxes and axles have all focused on engineering new products that exceed the Final Tier 4 emissions standards introduced between 2013 and 2015. The manufacturers work in conjunction with the makers of agricultural, construction and other off-highway vehicles to ensure the final product now meet the even tougher requirements of Stage V regulations that both consumers and governments demand.
Many vehicles now automatically monitor and optimise effectiveness while the vehicle is being operated to ensure maximum efficiency. Design engineers employ a variety of test methods during product development to ensure that these feedback systems meet the necessary performance standards. The two main methods used use to collect precise data for feedback systems are: strain gages; and torque transducers.
Strain gage-based transducers measure force and torque at the critical points within the system. With this method, an electrical signal from a battery is passed through a strain gage, which measures the strain or force in a given direction based on a change in the gage’s electrical resistance equal to the force applied, using the Wheatstone Bridge model. Measurements can be taken at multiple points, including an engine gear shaft, flex plate, transmission shaft, gearbox, axles, wheel hub assemblies, Power Take-offs and implements. By incorporating strain gages directly into the design of a drive shaft, for example, the vehicle management system can measure the rotational deflection or strain on the shaft while in use and correct the power delivery accordingly.
The Flexplate is an example of a drivetrain component that has been adapted to collect data for feedback systems. This solution offers a variety of advantages:
No need to install an additional transducer
Linearity and reversibility error of less than 0.1%
No change in the mechanical behavior of the drivetrain component
Continuous long-duration measurements
Wider range of operating temperatures
Robust transducer for continuous operation
Immune and insensitive to electromagnetic interferences (EMC)
Torque transducers offer another approach to measuring torque that employs the same principles as strain gage measurement. However, a torque transducer is a highly precise machined element that’s installed between two components of the system at the point at which the torque is to be measured. This transducer is specifically designed to focus the rotational force and torque being applied directly at sensing areas where the strain gages are located. Torque measurement instruments used to be expensive, bulky and sensitive which made them suitable only for laboratory testing purposes. However improvements in reliability and ruggedisation have enabled vehicle, engine and driveline component manufacturers to incorporate factory-installed, production-level torque measurement directly into their vehicles.
By combining live force measurements with Internet-of-Things commmunication, and ruggedised on-board computing with Artificial Intelligence software, vehicle management systems can not only sense power loss or gain at various stages of the driveline, the wheels and the implements, but also make adjustments automatically and in real time. The short term effect of the feedback loop is reduced stress onvehicle components, which avoids catastrophic failure. Long term the feedback loop optimises maintenance cycles, increases overall efficiency and reduces cost of ownership.
All of which paves the way for the newest stage in efficiency gains: the autonomous farming vehicle. In this economic model, one operator can control multiple autonomous vehicles remotely at the same time. No surprise then, that the demand for Autonomous Farm Equipment is set to expand rapidly.The global value of US $ 65 billion in 2020, is estimated to grow at 12% per annum, reaching US $ 135 by 2026.).
Although smaller, at US $ 2.3 billion in 2020, even faster growth – 23% per annnum is predicted for the global Autonomous Mining Vehicles market.
As the demand for higher performance from off-highway vehicles grows, the autonomous vehicle industry will see further advances in vehicle design, system maagement and still wider adoption. This in turn enables the off-highway industry to make further progress in the quest for lower emissions, fuel savings and vehicle stability control.
The OEM Sensors team at HBK plays a key role in these advances by providing the data that feeds the control loop. Since standard Sensors are seldome available in the size or format that Design Engineers require for a new vehicle, they turn to HBK for the design and ustom sensors.
HBK engineer adapt the design of individual components like flex plates, drivetrains, gear wheels or axles: they design custom strain gages and incorporate these into the components so that they become functional sensors that accurately measure torque, pressure, force or load. By embedding a telemetry board or induction ring into the components themselves, data can be transmitted wirelessly to the vehicle management system.
Vehicle manufacturers around the globe rely on our engineers to design sensors that meet their specific requirements; and on HBK manufacturing facilities on three continents to deliver the required volume, at the desired quality, on time.