Active Vehicle Safety Systems (AVSS) play a crucial role in reducing road-accident fatalities involving Heavy Commercial Road Vehicles (HCRVs), which predominantly use pneumatic brakes. The performance of these brakes is influenced by factors such as air compressibility, hose length, and inherently slower pressure-build characteristics. In current AVSS implementations such as the Antilock Braking System (ABS), pressure control is achieved using modulator valves that operate through binary ON–OFF solenoid actuation, commonly referred to as ‘modulation’. In this work, two actuator control approaches for pneumatic ABS are considered. The first is the conventional modulation, where the solenoid valves switch between apply, hold, and exhaust states without closed-loop pressure feedback. The second is ‘regulation’, the focus of the present study, where the brake chamber pressure is controlled in closed loop using feedback from an integrated pressure sensor. The objective of introducing regulation is to improve braking performance while ensuring that the control strategy remains computationally feasible for implementation on automotive-grade Electronic Control Units (ECUs). A PID-based Smith controller is developed for accurate regulation of brake chamber pressure, mitigating the effects of delay associated with the pneumatic brake system. Subsequently, the ABS with ‘regulation’ was made fault tolerant to multiple pressure sensor failures using Kalman filter for brake chamber pressure estimation. The algorithms were evaluated on an ECU integrated with a Hardware-in-Loop (HiL) setup having the pneumatic brake hardware interfaced with IPG TruckMaker®, a vehicle dynamics simulation software. The ABS with ‘modulation’ and ‘regulation’ were compared across varying load and road conditions, and the ABS with ‘regulation’ reduced stable braking distances by 11.6% on average, with 22.2% higher Mean Fully Developed Deceleration (MFDD), when compared to ABS with ‘modulation’. Moreover, the adverse effects of pressure sensor failure on ABS performance were significantly reduced with inclusion of Kalman Filter, while establishing consistency in ABS performance even with multiple sensor failures.
Jakka et al. (Thu,) studied this question.