Motion control for high end vehicle simulation

Its DIL solutions are available in a variety of form factors from test bench models with steering force feedback to highly dynamic six degree of freedom (6-DOF) simulators combining software, mechatronics, video and audio for a truly immersive multi-sensory experience.

Ansible´s DIL simulators are used for real time vehicle model development and cross-functional product development through to expert driver evaluation of simulated vehicle dynamics and electronics system tuning. Ansible has chosen Heason Technology as its motion control supply partner for high specification motors, drives, linear units and precision actuators that enable the simulations expert to deliver the high specification systems required by the automotive and motorsports industry.

Ansible introduced and patented its ´stratiform´ DIL platform in 2009 from a vision described by Kia Cammaerts, its founder and Technical Director, “To develop what an automotive style driving simulator should be, and how it should behave.” Working from the specific requirements to convince the most experienced test drivers and professionals, the Ansible design team use what they term as ´cues´ that cover all of the haptic, inertial and environmental inputs that are sensed in real time and are essential for completely assured driver perception.

In terms of a road vehicle simulation, this perception needs the hardware and software system to deliver each of these cues with millisecond level response times to the driver´s actions. Alternative concepts such as the Stewart Platform or Hexapod structures, though adequate for the relatively slow response times for aircraft simulation or the pseudo-realistic ´shaking´ experience of entertainment motion bases, just cannot deliver this level of accurate dynamic response. Such structures also require complex kinematic transformation algorithms even for simple moves such as straight line horizontal motion.

Mechanical system
Ansible Motion´s stratiform mechanical system is based on a series of stages using linear actuators that can individually deliver the intensity of acceleration and jerk which road level vehicles from racing cars to commercial trucks are subjected to in everyday situations. Each of several ground plane motion cues and other inertial cues are actuated by a separate motor with a typical dynamic simulator system such as Ansible´s Delta series having between six and 13 servo motion axes.

Phil Morse, Ansible´s Technical Liaison Engineer explained: “The first three stages of our stratiform deliver surge, sway and yaw, continuing to work upwards we encounter a 3-DOF parallel machine that addresses the remaining three vehicle motion axes - heave, pitch and roll. This describes the primary 6-DOF, and the remaining motors (numbers 7-13) are assigned to supplemental cueing devices such as handwheel torque feedback, seatbelt loading, helmet loading (in racing applications), pedal actuators, seat actuators and so on.”

This stacked geometry is essentially an X, Y, Z platform with multiple stages in each axis that move independently or with synchronous compound movements to produce all the motions required for convincing driver perception. Fore and aft movement is from the X-axis producing the surge element, side to side motion from the Y-axis produces sway, and linear actuators take care of Z-axis motion for heave or bounce. The ingenious linear mechanics include actuators to produce rotations around these linear axes to simulate pitch, yaw and roll. As opposed to the previously mentioned hexapod, as many movements are generated from a single axis, the system response is extremely fast, tethered directly to simulated vehicle physics, and the control is simplified.

Motion system
Ansible Motion developed its own EtherCAT master-based vehicle dynamics hardware and software platform that combines streamed motion commands into the stratiform´s servo drives completely coordinated with photorealistic graphic projection and surround sound. The complete system works in combination with multiple sensor inputs from the driver´s interaction - steering, accelerator, brake, clutch and gear selection etc. - with the capability to adapt the vehicle characteristics with model simulation of factors such as road surface, tyres, suspension or specific on-board electronic control system modelling. In this way, the complete system loop is effectively closed by the driver in the same way as if he or she is driving an actual vehicle.

Ansible Motion´s stratiform offers benefits on many levels. For driver evaluation or training, it can combine with inertial measurement units (IMUs) which precisely record the specific force and angular rates in real time to compare actual performance under driver control with the driver´s perception of performance. For driver experience and training, a real time laboratory control environment is made possible, where for instance a skilled racing driver can approach the same area of a circuit repeatedly with perfectly consistent conditions - honing and perfecting expertise, free from unknown factors which an actual race track with its unpredictable environment would not allow.

The benefits of the ability to monitor such an array of measurement channels and system/environment interactions from both the car and drivers point of view are obviously of great interest to the motorsports industry. For automotive vehicle and component manufacturers, using a DIL system has enormous benefits in accelerating product development with faster time to market and the ability to simulate all kinds of functional equipment for new vehicle design, model upgrades or modifications etc.