T-IBC (Onebox) Integrated Line Control Brake System

For smart new energy vehicles, traditional vacuum boosters combined with pump-controlled hydraulic systems (such as ESC and EPBi) are unable to address the vacuum source issue. 


These systems have drawbacks such as pressure control fluctuations and slow response times, which fail to meet the functional requirements of smart new energy vehicles. Additionally, considering the limitations of efficiency in piston pumps, pump-controlled hydraulic systems are not suitable for long-term operation. 


The T-IBC (Onebox) Integrated Line Control Brake System solution offers a complete integration of eBooster and EPBi functionalities. It provides advantages such as high integration, fast brake response, and precise control. This solution aligns with the urgent demands for advanced driver-assistance systems and fulfills the role of a core chassis component in smart new energy vehicles.


T-IBC System Solution


The T-IBC system is an electronic hydraulic line control brake system that integrates the pedal push rod, motor, transmission mechanism, master cylinder, hydraulic module, and redundant EPB (Electronic Parking Brake). 


During conventional braking, the hydraulic connection between the brake pedal and wheel cylinder is eliminated, showcasing the typical characteristic of hydraulic decoupling. 

The system features an independent drive motor as the conventional brake source. The pressurization method, utilizing a hollow shaft motor directly driving a ball screw piston module, results in a total assembly weight of approximately 5.3kg and pressurization efficiency exceeding 90%, meeting the braking requirements of medium and large passenger vehicles.


Furthermore, the T-IBC system is equipped with one displacement sensor and two pressure sensors as an assembly for monitoring the driver's braking intention and hydraulic model verification. 


The redundant sensor configuration provides a solid foundation for intent recognition, functional degradation, and redundant control, significantly enhancing system safety and functionality.


In the T-IBC assembly, during normal operating mode, the pressure in the brake wheel cylinders is completely decoupled from the driver's pedal input. 


The braking force of the vehicle is entirely provided by the motor. The hydraulic fluid in the pedal master cylinder, when the driver presses the brake pedal, does not enter the wheel cylinder circuit. Instead, it is pumped into a foot feel simulator composed of a piston-spring mechanism. 


This simulator provides the driver with simulated pedal feel and travel feedback during conventional braking.


The conventional braking process in this solution can be summarized as follows:


Driver inputs the brake pedal.

Signal from the pedal displacement sensor.

Recognition of braking intention.

Motor action drives the master cylinder piston to pressurize.

Brake fluid enters the wheel cylinders through a pressure-boosting valve.

Braking force is generated.


Key Technologies of T-IBC


Redundant Electronic Control Architecture Design


The T-IBC system incorporates a redundant electronic control architecture based on dual MCUs (Microcontroller Units) and redundant EPB (Electronic Parking Brake) control. 


The entire solution includes dual independent external power supplies, dual external CAN/CANFD communication, and redundant EPB control. The motor drive unit, motor position sensor, power management unit, and main control MCU are all implemented with a dual-redundant architecture.


The main control MCU utilizes a multi-core lockstep 32-bit chip, capable of supporting the highest ASIL-D functional safety level. 


Both MCUs are capable of complete EPB control and CAN communication functionalities, with the roles of master and slave allocated by default after power initialization. 


In the event of a single-point failure, the dual MCUs employ fault diagnosis and handling mechanisms to determine whether to switch the EPB control between master and slave. 


If necessary, the system switches from the slave mode to the master control system to ensure continued operation and system reliability.


Series Electromagnetic Valve Design


The precise control of hydraulic decoupling and wheel cylinder pressure in the T-IBC system relies on the collaborative action of 14 high-precision electromagnetic valves across 6 categories.

Traditional ESC (Electronic Stability Control) electromagnetic valves are not suitable for meeting the high-flow and precise line control requirements of T-IBC. 


They can result in significant pressure fluctuations in the wheel cylinders, aggressive active braking, and high-frequency opening and closing noise.


The performance of the T-IBC system fundamentally depends on the design level and manufacturing capability of the series electromagnetic valves. 


Based on the million-level production experience of ESC applications, Yingchuanghuizhi (Inno-Auto) has spent two years developing a new series of electromagnetic valve structures and processes that are tailored to the characteristics of T-IBC.


Vehicle Function Design


Due to the decoupling of the driver's direct braking circuit and the actual pressure build-up circuit in the T-IBC system, it provides greater design flexibility in terms of overall vehicle functionality. 


The T-IBC system can determine the driver's braking intention based on the degree and rate of pedal input. 


By calculating the motor's output torque, it can actively/externally generate the required pressure to meet the driver's intent. During this process, algorithmic compensation is applied for factors such as temperature, efficiency, and friction. 


This ensures optimal performance and responsiveness while considering the effects of various conditions.


Basic Brake Algorithm


The T-IBC system not only incorporates basic brake control functions but also integrates intelligent driver assistance systems that support multiple additional and value-added features. 


Through advanced sensors and intelligent control algorithms, T-IBC can continuously monitor the vehicle's status and driver behavior in real-time and make corresponding adjustments. 


For example, in the event of vehicle skidding or loss of control, the system can help stabilize the vehicle and enhance driving safety by precisely controlling the braking force and wheel cylinder pressure.


This ensures optimal control and improves overall vehicle stability and safety.


The development of electric vehicles aligns with the environmental requirements of the automotive industry and the strategic plans for energy development in many countries. 


The production and market share of new energy vehicles are increasing year by year. The integrated line control brake system has become the core execution unit in current intelligent electric vehicles due to its unique characteristics.


  • Integration: The mechanical master cylinder is embedded inside the valve block, reducing the vacuum and brake piping, resulting in reduced overall weight and smaller size, which is beneficial for vehicle space arrangement.


  • Pedal Feel Simulator: The addition of a pedal feel simulator allows for customization of dynamic and static pedal feel, meeting the varying pedal feel preferences of different customers.


  • Brake Decoupling and Stability Control: The system achieves brake decoupling and stability control, significantly improving the energy recovery efficiency of new energy vehicles.


  • Hollow Shaft Motor Direct Drive: The direct drive solution with a hollow shaft motor reduces transmission efficiency losses, resulting in faster response, more precise control, smaller size, and lighter weight for the T-IBC system.


  • Redundancy: T-IBC system can incorporate redundant brake units to meet the backup braking requirements for Level 3 and above autonomous driving functions.


Compared to traditional brake system configurations, T-IBC requires more complex system architecture and redundancy to ensure vehicle safety, reliability, and driving experience, which also presents higher technological barriers. It is believed that in the future, T-IBC systems will provide consumers with safer, more reliable, and more comfortable products.

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