Vehicle ride is a critical factor for Indian terrain as roads vary from national highways with a low level of waviness to rural roads with irregular bumps and droops. We will discuss some of the different evaluation methods that can be used for the assessment of ride comfort and ride quality and their test methodology.
- Vehicle Ride Quality: Vehicle Ride quality can be defined as the capacity of the vehicle to fulfil the transport requirements from the perspective of vibration level of exposure, depending on the vehicle type, number of goods or the engine operating conditions.
- Vehicle Ride Comfort: Vehicle Ride comfort analysis requires the effect of the mechanical vibrations upon the human body to be considered.
Multiple Components affect the vehicle ride, and below figure summarises the evaluation methods to understand the impact of various components on vehicle ride.
Environment for Vehicle Ride Evaluation
1. Uncontrolled Environment – This type of testing is done on real life road conditions with uneven bumps and irregularities. This area of vehicle ride testing will be discussed in future blogs.
2. Controlled Environment – In a controlled environment, we try to replicate the road conditions like single bump, multiple consecutive bumps, etc. depending upon the testing required as per the vehicle/user. This is a controlled input and this helps in correlating the behaviour of the vehicle with known inputs.
Vehicle Ride Evaluation Techniques
1. Vibration Dose Value: Vibration Dose is a parameter that combines the magnitude of vibration and the exposure time for which it occurs. When assessing intermittent vibration, it is necessary to use the vibration dose value (VDV), as it takes into account the frequency weightage factors that consider the human response to the vibrations. The VDV formulae uses the rms acceleration raised to the fourth power to evaluate the vibration levels. This technique ensures that VDV is more sensitive to the peaks in the acceleration levels. This method is used particularly for the evaluation of ride comfort.
2. Suspension Working Space: Suspension Working Space (SWS) is one of the factors that play a crucial role in understanding the response of the vehicle suspension system over a road surface depending upon the vehicle damper settings. It helps us to evaluate the maximum vertical suspension travel in the critical conditions. SWS helps in finding out the optimum suspension settings for a range of speeds depending upon the requirement of the user. This method is helpful in calculating the ride quality of the vehicle.
3. SEAT factor: The SEAT value is a measure of how well the transmissibility of a seat is suited to the spectrum of entering vibration, taking into account the sensitivity of the seat occupant to different frequencies. SEAT values less than 100% indicate isolation or attenuation of vibration. It allows for the comparison of seat performance on a variety of road surfaces. SEAT factor can be used for the assessment of driver and passenger ride comfort. It also tells us about the seat isolation performance of a vehicle at different speeds, i.e. how well the driver or passenger seat is able to minimise the vibrations reaching to the seat surface.
4. Vehicle Ride Diagram: A time domain measure based on peak-to-peak values is therefore created, and for different excitation levels, the values are calculated and then used to create a diagram. The calculation of the curves which define the ride diagram is basically a complex multi-step process. Vehicle Ride diagram is the only method that differentiates between the response of the vehicle vibrations due to transitional and stationary events for a range of speeds. This method is extremely helpful for the comparison of different vehicles of the same segment.
The selection of the suitable evaluation method for the vehicle ride assessment depends on the output received by the user and the ride parameter to be evaluated. The best method can be chosen as per the requirements and necessity of the user/customer.
The upcoming blog will focus and emphasize on the simulation and test analysis performed for the different evaluation techniques for ride comfort and ride quality explained in this blog.