In recent years, motorsport has increasingly focused on environmental concerns, leading to the rise of hybrid and fully electric competitions. In this scenario, electric motors and batteries take a crucial role in reducing the environmental impact by recovering energy during braking. However, due to inherent limitations, motors and battery cannot fully capture all braking power, necessitating the use of standard friction brakes. To achieve an efficient balance between electric motors and friction brakes, the brake pressure can no longer be directly controlled by the driver. Instead, it must be computed by the Vehicle Control Unit (VCU) and sent to a smart actuator, i.e. the Brake-By-Wire (BBW), which ensures that the required pressure is applied.
The standard approach to achieve precise pressure control is to design a nested Proportional-Integral-Derivative (PID) control architecture, which requires an accurate nominal model of the system dynamics to meet the desired tracking performance. However, in motorsport applications, actuator dynamics are complex to identify, car-dependent, and, most importantly, time-varying due to factors like temperature changes and wear. These challenges make PID controllers based on nominal models less robust, both in terms of stability and tracking performance.
To address these challenges, this paper proposes a robust architecture based on a cascade Linear Active Disturbance Rejection Control (LADRC) scheme for an electro-hydraulic actuator. The architecture consists of an inner loop, based on a second-order LADRC, which controls the piston position, and an outer loop, which employs a first-order LADRC to regulate the pressure. Compared to standard PID controllers, the LADRC approach promises two key advantages: it is faster and easier to tune while offering increased robustness. The proposed control scheme is experimentally validated on a test bench using a state-of-the-art BBW system and a racing car hydraulic line highlighting an increased robustness compared to a standard PID scheme.