Experimental Validation of Hydro-Pneumatic ABS System for Off-Highway Heavy Tonnage Military Vehicle

Braking system is having a key importance in vehicle safety & handling stability. In this research paper I had developed a circuit model of Antilock braking system where the operating medium is hydro-pneumatic. A solenoid operated modulator valve consisting of two 2/2 valves is connected in line with the air cylinder & hydraulic master cylinder assembly. Using methodology of response time calibration time taken to modulate hydraulic pressure against pneumatic pressure is evaluated. The signal input to the modulator valve is given by the Electronic controlled unit (ECU). All results obtained is exported to an excel file using Data Acquisition software with pressure myograph system. It gives easy and intuitive readings based on the signal program from ECU for various inputs (i.e. ramp, step). The signals are program for various inputs in order to check the fidelity of the circuit. These readings are easily customized to get the optimum graphs. The response time evaluated from the calibrated data is compared with benchmark or standard set by central motor vehicles rules (CMVR) to meet the regulation. To obtain the deceleration rate with stability of core hydraulic brake circuit in Dual air over hydraulic Circuit (DAOH) system for Off-Highway heavy tonnage combat vehicle this research proposal is being approached.

Usage of pneumatic foundation brake for multi-axle heavy vehicle with independent suspension for Off-Road driving condition has always been critical and challenging. Compactness, weight & mechanically moving components at the foundation were some of the drawbacks of core pneumatic brake system. As compressor of high capacity and discharge rate is readily available in the vehicle for auxiliary operation. But its efficiency was not fully utilized as per its designed capacity. The max pressure requirement for the hydraulic fixed caliper was calculated based on the vehicle inputs and the required deceleration rate for service application & parking regulations. The designed DAOH with hydro-pneumatic ABS and the component selected were meeting the pressure & performance requirement of the brake system eliminating the requirement of separate driveline & Hydraulic pump if core hydraulic medium of actuation was selected. This was additional advantage for compactness & overall cost of the system. The practice of this theory will add a qualitative research in the field of braking dynamics and ABS circuit design and development.