Automotive FAQs

Vehicle testing can refer to diagnosing faults at your local garage to full blown development testing in Formula 1. Testing generally refers to the evaluation of prototype vehicles by manufacturers to determine functionality & performance.

CAN-bus systems are now acknowledged as the automotive industry's standard format used to transmit information around vehicles;interconnecting the ECU's and Sensors which are vital to monitor and control all aspects of a modern vehicles systems. CAN is also used as the system-bus throughout our range of data acquisition units and sensors.Our data loggers also have the capability to link to the CAN-bus network on-board a vehicle to log and verify CAN-bus data "traffic".

Pitch 'n' Roll ..... Explained Vehicle pitch and roll angles can be determined by measuring the distance between three car-body points and the road or track surface. This process requires an exact knowledge of the geometric arrangement of the sensors. Calculation of Pitch and Roll is an iterative process. Therefore, it is not possible to calculate pitch and roll angle independently of each other. Error estimation shows the influence of the different measurement parameters on the results. The CORREVIT(r) Pitch and Roll System is designed to precisely determine the position of a vehicle relative to a road or track surface. This advanced measurement system incorporates three optical sensors mounted to a vehicle, each of which provides individual dynamic measurements of the distance between the vehicle and the road or track surface. Several sensor mounting configurations are possible, however it must be noted that each of these configurations requires distinct calculations to determine pitch and roll angles. This overview also provides an analysis of possible sources of error and indicates which of the measurement parameters will have the greatest influence on accuracy.

The common term of understeer / oversteer is really a measure of the SLIP ANGLE of a vehicle. Does the vehicle slip at the front or back or both?

MFDD - Mean Fully Developed Deceleration. There are a variety of ways to calculate deceleration using speed, distance and time formulae. The braking of a vehicle is greatly influenced by the initial braking system response to the pedal depression and the pitching of the vehicle,especially at low speed. The MFDD calculation starts at 80% of the start speed and stops at 10% of the start speed, this attempts to negate the effects mentioned above. Now some equations! The acceleration data may be calculated by different formula: 1/. a(v,t): (Ve - Va) / (Te - Ta): 2/. a(v,s):(Ve^2 - Va^2)/((Se - Sa) *2) 3/. a(s,t):2 * ((Se - Sa) / (Te - Ta)^2 - Va /(Te - Ta)) The MFDD (mean fully developed deceleration) is displayed only after deceleration tests. This value is calculated using the data between 80% and 10% of the start speed. You should enter the desired start and end speed (for example 100 and 0 km/h) in the test configuration. The test also works if it is started either by an external trigger or manually. The end speed should be set to 0. The formula of the MFDD-value is: a_mfdd: ABS (( v_01^2 - v_08^2 ) / (( s_01 - s_08 ) * )) with v_01 = 0.1 * (startSpeed-stopTrigger) if startSpeed > stopTrigger or 0.1 * (startSpeed) if stopTrigger > startSpeed v_08 = 0.8 * (startSpeed-stopTrigger) if startSpeed > stopTrigger or 0.8 * (startSpeed) if stopTrigger > startSpeed s_01 = distance in time of v_01 s_08 = distance in time of v_08 So now you know!

Data logging, or data acquisition to give it it's posh name, not only measures parameters from various sensors around the car, it also records the values,usually against time.

Data logging is purely the collection of data, although we see that there are two distinct areas: 1 - Time based data logging: this is normally used for long term data collection when vehicles are being monitored during extensive durability tests. The data can be gathered onboard and/or sent to a central base using GPRS connection. 2 - Specific data logging: this is where there is a defined start and stop condition to the test, brake and acceleration tests for example. The data logging is started on a pre-defined parameter such as speed or switch and is stopped on a different parameter e.g. brake tests from 100 kph to rest.

Roll angle 'g' is the angle between the transversal axis (y-axis) of the vehicle and the projection of that axis to the road. 'g' exhibits positive values when the vehicle rolls to the right, and exhibits negative values when the vehicle rolls to the left.

Pitch angle 'b' is the angle between the longitudinal axis (x-axis) of the vehicle and the projection of that axis to the road. 'b' is a positive value when the vehicle pitches forward, and a negative value when the vehicle pitches back.

The co-ordinate system for the test vehicle is defined in accordance with the DIN 70 000 standard. Each of the three co-ordinate axes (x, y and z) originate at the vehicle centre of gravity and coincide with the three main axes of inertia: The positive X-axis corresponds to the vehicle longitudinal axis, pointing forward. The positive Y-axis corresponds to the vehicle transversal axis, pointing left. The positive Z-axis corresponds to the vehicle vertical axis, pointing upward. Using your right hand,point your index finger forward (X-axis),your second finger at 90 degs (Y-axis) and your thumb up (Z-axis).

CORREVIT Principle is the operating principle behind the optical sensors that we supply. The principle was initially devised by the Leica company in Germany over 20 years ago and has been the basis of the Correvit sensors ever since.

The MicroSAT produces a data file (*.R1) which can be read in either MS History or the 2D 'Race' software. The MS History is a basic package allowing you to produce a latitude vs longtitude graph. The 2D 'Race' software for the microsat is a cut down version of the full racing analysis package, the software is free issue when you buy a microsat. The software will allow you to create track maps and analyse the GPS data that you logged.

GPS alone will not give you accurate slip angle as you cannot get the seperation required when using two antennae. The other significant problem with using GPS is that effectively you will measure the slip angle at the roof, not much use to chassis engineers ! The only way to really measure SLIP ANGLE correctly is to combine the GPS with an Inertial Navigation System, we have the answer. The RT range of systems will give you slip angles at all 4 wheels if you require it, in addition to the body slip angles. Give us a call and we will discuss your application with you.