One of the most challenging applications for advanced motion control is in the area of testing vehicles. Today, in automotive testing, virtually all-subjective driver feedback necessary for vehicle, module, or even component development is gathered on the test track. Test track work is both expensive and inefficient. To overcome these deficits, Moog FCS is pioneering a combination of “hardware-in-the-loop” and “human-in-the-loop” simulation (H2IL), and thereby significantly reducing the amount of test track work during development. This will lead OEMs and automotive tier suppliers to shorten product development times and reduce the costs of testing.
Hardware-in-the-loop (HIL) testing describes a process where actual vehicle hardware components are tested in an otherwise simulated environment. Using this technique, the simulation interfaces with the hardware under test to create a normal operating environment for the hardware. The interface can be hydraulic, electric, mechanical, or in fact, any interface necessary to accomplish the objective of simulating the operating environments of the component. This may also include use of environmental chambers to simulate temperature, humidity or air even air pressure.
Moog FCS has extensive experience in the complex simulation of precise movement in areas such as flight simulation and testing. From servocontrollers and software with advanced algorithms to superior control loading actuators. This competency is key in many of the systems built today and positions Moog FCS as a key supplier of testing systems.
Background on H2IL
Hardware and human-in-the-loop testing has been employed for many years in the aerospace world to reduce research and development time. In doing so, new prototype components can be developed and validated on a test system under real working conditions together with a human being in the test to get actual pilot response and perception.
Most people are aware of human-in-the-loop simulation used for training purposes in aircraft flight simulators. In this case, the human is the only non-simulated “part” of the chain; no real aircraft parts are used.
A more real scenario is when engineering simulators are used to combine human-in-the-loop with hardware-in-the-loop testing. One of the obvious reasons to take this approach is that no pilot would want to fly an experimental piece of new hardware before getting some confidence in its performance. Equally important are cost considerations associated with aerospace developments where prototypes can cost tens of millions of dollars.
The hardware-in-the-loop/human-in-the-loop or H2IL simulators range from simple mockup cockpits to test out a new on board computer, to full “iron bird” rigs where a complete aircraft representative structure is outfitted with all moving parts normally found on the aircraft.
For the safety of the testing personnel a flight simulator is used. All the parts in the simulation actually represented in hardware are coupled into the simulation at a sufficiently high frequency so that their response mimics the bandwidth of the simulated events. Actuators are coupled to the “iron bird” surfaces to simulate the aerodynamic loading. If one of the surfaces is blocked on the rig, the pilot will feel a blocked control as a consequence. Moog FCS has delivered such systems to the aerospace industry for many years.
H2IL Testing for Automotive Applications
Consider the application presented above: traditional hardware-in-the-loop testing e.g. powertrain. The powertrain is still driven (or tested) on a dynamometer. By replacing the simulated driver input with a full 6 degrees of freedom (DOF) motion simulator and an actual driver (human) in the loop, we create the hardware-in-the-loop/human-in-the-Loop (H2IL) simulation. In the H2IL testing scenario, the driver of the motion simulator drives a vehicle model on “mapped” proving ground roads while the powertrain operates on the dynamometer, now coupled to the motion platform. As illustrated below in Figure
In an H2IL configuration, the initial automotive system development can be brought into the laboratory. Here are a number of advantages that may be achieved compared hardware-in-the-loop testing:
- Immediate Driver Response: Drivers respond instantly and give qualitative feedback on the direction of a solution. Evaluating the differences between multiple drivers can provide instant feedback. By recording driving habits for given conditions on this new design, objective driver metrics can be developed.
- Track Time Reduction: New scenarios can be created and recorded for playback without ever leaving the lab. With the ability to simulate track surfaces, ambient conditions and vehicle models, virtually any road or climatic conditions can be simulated. Development time and test time are dramatically reduced and controlled because we no longer require access to the track or proving grounds and we no longer have to wait until climatic conditions are correct. For example, rainy days can be avoided or repeated over and again.
- Allowing Component Modification: Often it is desirable to study vehicle response to one specific road condition. Using these technologies the same road section can be replayed over and over while making subtle system changes, allowing fast, repeatable A-B-A testing.
- Increased Test Driver’s Safety: Dangerous road conditions can be tested in safer, more controlled environments. Drivers will not be subjected to dangerous road or ambient conditions since they will be operating the simulator. Track scenarios may be taken to the limit of performance on the new design but safety limits in the simulator will protect the driver and even the test parts from uncontrolled or out of control responses.
- Exact Replicability: Driver aids can be deployed to improve driver performance or train drivers to perform specific maneuvers. The performance of each lap can be recorded. Deviations to this lap performance can be observed as vehicle hardware is modified or swapped. Laps can be superimposed on screen so a driver has reference to previous performances. This can aid a driver in operating the “vehicle” on a certain part of the track consistently and repeatedly. If a component does not respond well on a certain part of the track, just that part of the track can be evaluated repeatedly while recording the results. This can offer strong driver evaluation especially in racing scenarios.
Summary
H2IL testing is a truly viable form of validating design of vehicles and vehicle components. This is a process that has been employed for many years in the aerospace industry and will prove to be the way of the future for the automotive industry. As proving ground and track time becomes more costly and as shortened program timescales drive parallel development to become the norm, the need for H2IL will become more interesting and important to the OEMs and automotive tier suppliers, not to mention race teams. Moog FCS has effectively served this industry because of both the simulator and testing equipment expertise and the range of advanced motion control solutions we offer to the marketplace.
Author
Jan van Bekkum is was one of the founders of the former FCS (now Moog FCS) and worked for more then 15 years in the test system industry both in Holland and the US. Originally being responsible for aerospace test product development, he later moved to automotive testing product development. He studied technical computer science in Amsterdam.