CAN Protocol-Based Modeling of Vehicle Comfort System

Abstract

Automatic climate control systems (ACCSs) presently used in vehicle are based on the human sensory response and builds using most of electronics components for efficient operation. The analog driver and vehicle interface are used in Indian vehicles for indicating various states of vehicle such as temperature sensor readings, vehicle speed, fuel level, and HVAC mode. The optimized ACCS present in this paper is developed using math-based model of vehicle and CAN protocol. A commonly used protocol for serial communication is a controlled area network (CAN) bus protocol. The devices within a vehicle can communicate with each other using CAN without host computer. It is a multi-master broad cast bus standard. The devices connected through controlled area network are sensors, actuators, airbag sensor, antilock braking system, adaptive cruise control system, etc. CAN takes mode from driver of vehicle and also takes feedbacks from sensor connected within the vehicle and controls the heating, ventilation, and air conditioning (HVAC) in the vehicle. This paper presents system which is designed in MATLAB state-flow, and CAN messages used are designed using CAN DB++ editor. MATLAB vehicle network toolbox is capable of handling CAN messages in DBC file format. The system proposed in this paper, comprises of four blocks. First block allows user to select HVAC mode; its output selects the internal HVAC mode. According to that mode, blower speed and blower opening blocks produce their output. When driver selects HVAC mode, this activates internal CAN bus message by taking feedback from temperature sensor, fitted inside the vehicle, and sets internal mode as per temperature reading. There are total seven internal HVAC modes are provided; out of these, three are for controlling AC temperature, three for heater, and one is comfortable mode. Comfortable mode turns on either user make it on or any other mismatch in setting happens. It is a default mode of HVAC system. In blower speed block, amount of air blown inside the vehicle and whether that air is hot or cold is decided. As per speed of air decided by this, block control signal messages are generated. Next block is blower opening; in this block, flap angle of the blower is decided. The simulation results of system are observed on display block of MATLAB and messages generated by each block. When system satisfies all the control algorithms, it will be downloaded in test vehicle for testing confirmation and calibration. This system is time saving and cost-effective. If electronics components are used to build control logic, it will leads to many single line hardwired dedicated connections. In addition to increased cost, fault diagnostics and repair create a problem, at manufacturing and service. Use of CAN removes all the drawbacks and help system running in efficient manner and without transmission losses. In this system, error detection and correction mechanism are designed very strongly; if error occurs, all settings are resumed to default. The self-diagnostic capability of CAN prevents mishaps to be happen. Further, functionality can be improved by allowing other systems to be conjoined with existing system.