A load-based tire inflation system for a heavy-duty vehicle comprises at least one source of fluid pressure, suspension structure of the heavy-duty vehicle, a tire and wheel assembly and a system to control fluid pressure in the tire and wheel assembly. The suspension structure is located between a frame member and an axle and has a condition indicative of a weight of the heavy-duty vehicle. The tire and wheel assembly is operatively mounted to the axle and is in fluid communication with the source of fluid pressure. The control system controls fluid pressure in the tire and wheel assembly in response to the condition of the suspension structure.

A method for ascertaining the instantaneous roadway roughness in a vehicle. In the method, the frequency-dependent amplitude response is determined from the wheel speed, and a roughness characteristic variable is ascertained as a measure of the roadway roughness.

A method of setting the rides height of the air springs and air pressures of the tires, including receiving a user selected setting or preprogrammed ride height settings; sensing a ride height of, and air pressure within, each of the air springs; determining the weight of the vehicle based on the sensed ride height and air pressure within each of the air springs; providing specified ride heights for the left and right front and rear air springs; determining specified air pressures for the left and right front and rear tire inflators, based upon the determined weight of the vehicle and selected setting; inflating the left and right front and rear air springs to the specified ride heights; and inflating the left and right front and rear tires to the specified air pressures.

A regulator for establishing outlet fluid pressure. The regulator includes a valve body having a fluid pressure inlet in selective fluid communication with a fluid pressure outlet. A pilot pressure inlet is formed in the valve body and in fluid communication with a source of pilot pressure. Valving structure in the valve body establishes outlet fluid pressure as a function of pilot pressure. First adjustable structure within the valve body may establish a minimum outlet fluid pressure threshold without regard to pilot pressure. Second adjustable structure within the valve body may establish outlet fluid pressure offset relative to pilot pressure.

A vehicle height adjusting device includes a vehicle height adjusting unit, a prediction unit, and a vehicle height control unit. The vehicle height adjusting unit adjusts a vehicle height to one of a first state and a second state. In the first state, the vehicle height is set to a predetermined height, and in the second state, the vehicle height is set lower than the first state. The prediction unit predicts whether a drive battery (lower portion) of a vehicle interferes with a road surface in the second state. The vehicle height control unit controls the vehicle height adjusting unit to set the vehicle height to one of the first state and the second state. When the prediction unit predicts an interference between the drive battery of the vehicle and the road surface, the vehicle height adjusting unit restricts a transition from the first state to the second state.

A system for testing a suspension system of a vehicle includes an inertial measurement module and a suspension fault detection module. The inertial measurement module is configured to, while the vehicle is not moving, collect sensor data from one or more inertial measurement sensors for different states of the suspension system. The sensor data is indicative of inertial states of the vehicle while the suspension system is in each of the different states. The suspension fault detection module is configured to, based on the sensor data and a set of thresholds, determine whether a fault exists with the suspension system, isolate and identify the fault, and perform a countermeasure based on the detection of the fault.

A load based tire pressure regulation system for trucks or trailers employing an air spring maintained at a variable pressure P.sub.AS depending upon the load on the truck or trailer, includes an air pilot pressure regulator receiving air at pressure P.sub.AS and air at the pressure of at least one tire of a truck or trailer, and configured to feed air to and bleed air from the at least one tire of the truck or trailer as a function of the load on the truck or trailer. The pressure regulator is configured to feed air to and bleed air from the at least one tire of the truck or trailer based upon the pressure of the air spring P.sub.AS as a function of the load on the air spring (F.sub.AS), and further upon the recommended pressure P.sub.T of the at least one tire as a function of the load on the tire (F.sub.T).

A vehicle height adjusting device includes a vehicle height adjusting unit, a prediction unit, and a vehicle height control unit. The vehicle height adjusting unit adjusts a vehicle height to one of a first state and a second state. In the first state, the vehicle height is set to a predetermined height, and in the second state, the vehicle height is set lower than the first state. The prediction unit predicts whether a drive battery (lower portion) of a vehicle interferes with a road surface in the second state. The vehicle height control unit controls the vehicle height adjusting unit to set the vehicle height to one of the first state and the second state. When the prediction unit predicts an interference between the drive battery of the vehicle and the road surface, the vehicle height adjusting unit restricts a transition from the first state to the second state.

A method of setting the rides height of the air springs and air pressures of the tires, including receiving a user selected setting or preprogrammed ride height settings; sensing a ride height of, and air pressure within, each of the air springs; determining the weight of the vehicle based on the sensed ride height and air pressure within each of the air springs; providing specified ride heights for the left and right front and rear air springs; determining specified air pressures for the left and right front and rear tire inflators, based upon the determined weight of the vehicle and selected setting; inflating the left and right front and rear air springs to the specified ride heights; and inflating the left and right front and rear tires to the specified air pressures.

In various aspects, the performance optimization system described herein optimizes vehicle performance through smart alerts communicated to an operator, owner, or fleet manager of a vehicle. When a vehicle characteristic is outside of the target range, a smart alert can be communicated to the user to encourage the user to bring the vehicle characteristic back into a target range. Aspects of the performance optimization system can focus on tire characteristics, which are one type of vehicle characteristic. Exemplary tire characteristics can include tire pressure, tire tread, and tire alignment. In order to generate smart alerts, vehicle information can be gathered from a variety of sources. In particular, information about a tire can be collected from an onboard tire pressure monitoring system, tire mats, or other mechanisms. This information can be analyzed to determine whether vehicle characteristics are inside or outside of a target range for the particular characteristic. When outside the target range, a smart alert is generated.