Driver-In-The-Loop for Off-Highway Development

June 1, 2023

Dennis Marcus

Driver-in-the-loop (DIL) simulators have become an essential tool for passenger-car OEMs and suppliers, for cutting development time and cost and delivering a better product. In the past 20 years, the driving simulator has evolved from a vehicle-dynamics tool mostly used in a motorsport or high-performance context, to an essential component of the development landscape – a focal point that interfaces seamlessly with other engineering tools to deliver effective advanced driver assistance systems (ADAS), human-machine interface (HMI) and more. Engineers and management teams can get behind the wheel of a prototype vehicle much earlier in the development cycle and reduce the number of physical prototypes.

As in the motorsport world, DIL simulators have long been deployed by industrial and agricultural machinery makers as operator training tools. Now, forward-thinking OEMs and suppliers are starting to adopt them for engineering applications, too. Last year, simulator designer, manufacturer and integrator Cruden, which is based in the Netherlands, delivered its first simulator to a large multinational industrial and agricultural vehicle manufacturer.

This simulator, in combination with a hardware-in-the-loop (HIL) test system, is being used primarily to validate tractor cabin ECUs (electronic control units) and HMI. The complex HMI of a tractor cab must be easy to use but also integrate seamlessly with any number of implements from multiple suppliers.

Simulating a tractor

The hexapod motion system selected for the simulator has the necessary payload capacity to carry a full tractor cab mockup on its top platform. The configuration enables cabs to be switched out depending on which tractor is being tested. With the physical cab in place, its ECUs, screens and operator controls are integrated with a plant model of the entire tractor so that the DIL can virtually pilot the tractor while testing and validating the electronics.

The simulator, located in Europe, also is used in a vehicle-dynamics application to assess ride comfort. To facilitate this, Cruden created a digital twin of the manufacturer’s proving grounds so that real and virtual tractors can be driven repeatably on the same test tracks. Not only can the comfort of new tractor designs be assessed in the simulator, but back-to-back comparisons can be made with competitor vehicles, too. After recording rivals’ performance over the bumps in instrumented drives on the actual proving ground, the benchmarks can be replayed on the simulator.

This benefits the engineering team during development, as well as members of management during sign-off. Both groups can easily compare the performance of a new design to that of the competition. In the future, the simulator could even be used for target-setting at the start of a development program, as already practiced by some of Cruden’s automotive customers in the NVH (noise, vibration and harshness) domain.

Automated operations

There are many simulators active in the development of automotive ADAS and AV (autonomous vehicle) systems, both for product development and at universities engaged in human-factors research. The industrial and agricultural sectors are in many cases further along the path to connected and autonomous vehicles than is the case with passenger vehicles. Agricultural machines, for example, are loaded with sensors and must have complex, agnostic interfaces with third-party implements.

Many fatigue-reducing innovations in autonomy are in production or under development. Intelligent, GPS-based systems steer tractors autonomously for hours at a time after calculating the optimum path for the given duration and yield parameters. When harvesting, automatically coordinating the movement of a combine with a grain trailer reduces the need for a skilled operator to be available to drive the tractor.

A driving simulator is a very relevant tool to test these types of innovations, quickly and in total safety. Simulators have a proven track record in developing not just the physical controls and HMI, but in testing at an early stage the required handovers of control between operator and machine as well as the associated monitoring and alert systems.

An agnostic approach is taken when integrating cabin electronics and third-party engineering tools such as HIL systems, vehicle-dynamics models and also biometric tools such as an eye tracker. Integrations are tailored to the use case and to whichever tools the customer needs to support its development programs.

At power hydraulics specialist Danfoss, its first simulator installation located in northern Germany is configured to develop and demonstrate to its OEM customers new innovations in construction-equipment joystick control.

Another Cruden customer simulates the operation of a front-discharge concrete mixer truck using a DIL system. In the future, the company envisages more extensive engineering use of driving simulators in the construction-equipment industry to reduce the need for costly physical prototypes.

Future possibilities

The industrial and agricultural machinery sectors are just getting started with driving simulators in engineering applications. The visual system on the aforementioned tractor simulator, for example, is a relatively basic projector setup, whereas 360-degree visual systems and LED walls already are in place at automotive simulation facilities.

The need to monitor what’s going on behind a tractor means that more-enveloping visual systems may feature in future installations, but extended reality (XR) may offer an alternative to conventional visuals in applications where driving dynamics are secondary to effective machinery operation. The need for the driver to look down, ahead and behind differentiates many off-road situations from those on-road, for which simulator drivers typically require only a limited “letterbox” field of view. An XR head-mounted display (HMD) could prove to be an efficient and flexible way to extend the vertical range of an off-highway simulator’s visual system.

Such a concept could work well with a standard top platform that Cruden has under development. This would create a simpler and more flexible simulator by eliminating the need to mount the entire cab to the platform. Instead, just the seat and controls could be installed, enabling the driver to interact with the tractor or other off-highway machine in an immersive virtual realm.

Dennis Marcus, business development manager at Cruden BV, wrote this article for SAE Media as part of the annual Executive Viewpoints series.

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