Accelerometers, Force Sensors, Load Cells, Signal Conditioners, and Human Vibration Monitors
Driveability is a vehicle’s response to driver input through a series of drive cycles and is generally indicative of the degree of smoothness and steadiness of straight line acceleration and deceleration. Vehicle handling is also defined as a vehicle’s response to driver input; however, the emphasis is on vehicle motion transverse to the primary direction of motion, particularly during cornering, lane change maneuvers and its ability to maintain the chosen path. The low frequency response of the vehicle to driver input defines the “character” of the vehicle and is the basis for the image and branding of particular vehicle types. Primary and secondary ride are important aspects of ride quality and development of their performance is often a compromise with vehicle handling attributes.
Although driveability and ride & handling are unique attributes, they share some commonality. Measurement for both attributes is conducted using low frequency measurement instrumentation. Primary ride is typically measured in the 0 to 3 Hz range, while secondary ride is higher, but typically less than 25 Hz. Driveability and vehicle handling require measurements down to DC, as changes in vehicle motion by driver input are the primary metrics. With advancements in engine and vehicle technologies, it is now common practice to collect not only vehicle motion data but also system information from the vehicle’s CANBus, to monitor and adjust engine operating parameters, advanced combustion control (cylinder deactivation algorithms), stability control (brake and torque-based systems), and traction control, as these systems can play a significant role in driveability and ride & handling performance.
Driveability can be a complex equation between driver expectation and how a vehicle actually performs over numerous maneuvers in a particular drive cycle. While parlaying objective measurements into subjective ratings is still very much under scrutiny, the process of collecting objective data is noncontroversial and plays a crucial role in the vehicle development process.
Typical test setups include measurement of driver input and low frequency vehicle response, including:
- Pedal force (brake, accelerator, and clutch)
- Longitudinal vehicle acceleration
- Vehicle pitch
- Throttle position
- Turbo boost pressure
- Brake pressure
- Transmission shift parameters
Calibration engineers routinely strike a balance between fuel economy, NVH, and driveability performance by optimizing engine combustion processes and transmission shift schedules.
Ride & Handling
Vehicle manufacturers strive to achieve optimal vehicle handling and to balance handling performance against other key attributes in chassis development, including ride comfort; road noise; and durability, in accordance with brand status. Vehicle handling is a complex interaction between driver and vehicle; actions and reactions of a driver, including acceleration/deceleration, brake or clutch operation, gear shift, and steering movements. Vehicle specifications and trim levels also play a role in handling, including vehicle weight distribution; suspension; tires and wheels; electronic stability control; and more. Numerous testing situations take into account different driving styles, from defensive to aggressive, as well as weather and road conditions. Track-based testing includes:
- Step Steer
- Steering Pad
While these tests are performed for benchmarking against baseline targets, they are also used for gap analysis during the development stage, and occasionally performed to satisfy safety regulations prior to market release.
Vehicle handling tests lend themselves to be somewhat subjective. PCB® accelerometers and accessories can help achieve specific objective measurements to aid in vehicle handling analysis. PCB® sensors are small, lightweight, and hermetically sealed, making them waterproof to accommodate typical track environments.
PCB Piezotronics offers a complete line of sensors and instrumentation for vehicle driveability and ride & handling tests. Single axis and triaxial DC response accelerometers are designed to measure low-frequency vibration and motion. These units are inherently insensitive to base strain and transverse acceleration effects, and offer better thermal stability, higher overload protection, better signal-to-noise ratio, superior durability, and simpler test setups than strain gage-based DC sensors. Series 3711 and 3713 units are rugged by design; housed in titanium and hermetically sealed; and offer a single-ended output signal for each channel with power and ground leads. Series 3741 are precision units that offer a differential output signal for common-mode noise rejection. Model 356B41 triaxial, ICP® seat pad accelerometer measures whole body vibration influences associated with vehicle operation. The unit houses a triaxial accelerometer within a molded rubber pad that can be placed under a seated person or beneath a weighted test object. Model HVM100 human vibration meter utilizes accelerometer inputs to provide vibration severity measurements relative to human vibration exposure and is used with the seat pad accelerometer. Additional ICP® , triaxial accelerometers with high sensitivity, low frequency capability, and good resolution are available to aid in driveability and secondary ride measurement requirements. Series 1515-106 pedal effort force sensor is compact, lightweight, and designed to measure load applied to the brake, accelerator, and clutch pedals during acceleration, deceleration, and transmission shift events. Series 8161 and 8162 strain gage signal conditioners are used with the pedal effort force sensor. PCB® products are designed and manufactured in state-of-the-art facilities, and together with our global distribution network and Total Customer Satisfaction guarantee, you can rely on us to deliver products and solutions for your demanding requirements.