CarMaker/HIL-Simulators for Distance Control Systems
Mention virtual test driving with CarMaker ® and CarMaker/HIL by IPG, Software-in-the-Loop/Hardware-in-the-Loop for chassis and drivetrain control systems will probably spring to mind, as well as vehicle dynamics applications in relation to handling design. This is understandable given the numerous CarMaker/HIL simulators used by OEMs and premium suppliers for series and pre-development applications. The range extends from braking systems (ABS, ESP, BBC, EMB/EHB, EPB) and control systems in the drivetrain (TCS, EDS, ETM) and chassis (ESS/CDC) through to steering systems (AFS/EAS, EPS).
In all the cited applications, a virtual vehicle driven along a virtual road by a virtual driver generates virtual sensor signals as inputs for control systems which determine the vehicle's handling. The virtual vehicle also reacts realistically to interventions by these control systems. To date, the focus has usually been on observing the individual vehicle and its reactions to controller outputs and disturbance variables.
However, growing importance is now attached to a different category of control systems - and with it to MIL, SIL and HIL applications - requiring the modelling of both mobile and stationary environment objects. This category includes all those systems which detect and process objects in the vicinity of the vehicle, e.g. ACC, lane change assistant, parking systems and precrash systems designed to activate passive safety elements. Although such systems may not always influence the vehicle handling, they always have to be checked to ensure that they handle safely in realistic driving situations.
Experience shows that HIL solutions for systems with detection and processing of environment objects are highly individual and differ greatly. Hence the software used for object simulation purposes is an important element, but is not sufficient in itself for a seamless, all-in-one SIL/HIL solution. Only the engineering know-how acquired by the solution provider as a result of completing numerous successful HIL projects provides the customer with the certainty of being able to make speedy and productive use of an HIL simulator tailored specifically to his requirements and delivered on schedule.
And exactly this comprehensive know-how of HIL is, what IPG Automation offers its customers.
Let us start by taking a look at what features the CarMaker ® simulation environment by IPG Automotive offers developers of systems with object detection.
Several software components are responsible for incorporating environment objects in the CarMaker ® environment. The core component is the Obstacles feature which is an integral element of the CarMaker ® Model Library. The properties and movements of the obstacles are defined in a special menu in the CarMaker ® GUI. Two modes of animation are available for visualising simulation scenarios: special extensions in the IPGMovie ™ animation program provide a 3D presentation of the driving situation whilst another animation tool supplies a 2D presentation of a typical sensor wedge from a bird's eye view.
The Obstacles feature calculation module is incorporated in the CarMaker ® simulation program. It manages all static and mobile objects, and also takes care of moving the objects. It further determines the environment objects located in proximity to the virtual sensor. For each of these objects, the Obstacles functionality provides the information which are needed by the sensor model.
The obstacles are divided into two categories, static and mobile. Static objects include, for example, crash barriers, signs or bridge piles. As a general rule, the user will take account of the static objects relevant to his particular case, because, for example, the sensor system is deployed to differentiate between stationary and mobile objects. The mobile objects are generally vehicles driving ahead, or in the oncoming direction.
In the simplest case, the objects are cuboids with a reflective surface which can be parametered in terms of size and reflective properties. One can, however, extend the configuration to have other geometric bodies, or several reflective surfaces per body. The user defines the colour of the cuboid as an attribute for the animation. If necessary, user-defined graphic objects can be used at reasonable cost instead of the basic geometric bodies.
The movement of the objects is defined in a very flexible manner for each separate object. The object's position, speed, acceleration and crosswise deviation over time from the chosen lane can be set out in a table. The movement can alternatively be defined using a path-based, or a mixed time/path-based approach. The movement can additionally be overlaid with a sine function, trigonometric function or random function, both in the direction of travel and crosswise to the direction of travel. As the direction of travel of each object can also chosen (oncoming traffic), these definition options allow the operator to construct a full range of conceivable driving scenarios.
The simulated driving situation can be viewed with IPGMovie ™, the CarMaker ® tool for 3D animation. IPGMovie ™ automatically (dynamically) generates the graphic objects to be represented and updates the 3D view accordingly. Of particular interest to developers of sensor systems is the possibility to represent object-specific output factors of the sensor simulation in the animation online, i.e. during the simulation. Thus, for example, detection by means of a radar beam or a certain evaluation of the object by the sensor model can be directly depicted by having the 3D object change colour.
In addition to the 3D animation, processes and system states can also be followed and interpreted in 2D mode. If this is the case, a sensor wedge is usually shown from a bird's eye perspective. Shown in this way, the vehicle is portrayed as if fixed in position and the road and environment objects are shown in their movement relative to the vehicle. In this mode of presentation events are replayed "from the sensor's viewpoint", so to speak.
So what are the special features of the IPG solution?
The customer will certainly be pleased to find that the obstacle functionality is an integral part of the CarMaker ® software package, and not an add-on or an option to be purchased at extra cost. This gives all customers - those with the offline version of CarMaker ® and those with CarMaker/HIL - access to obstacle functionality, even in the very competitively priced basic edition. From a technical applications point of view, considerable advantages are gained by dovetailing the Obstacles feature with the road model, IPGRoad ™, used in CarMaker ®. Vehicles can easily be made to cover very long, realistic 3D distances (50 km and over) - in spite of these distances the obstacles can still easily and clearly be arranged and moved along the road and relative to the reference vehicle.