"Real-time control software Design" first week of work

Take the car ABS system to do case analysis:

Working principle: In the braking, ABS according to each wheel speed sensor transmission speed signal, can quickly determine the wheel of the holding of the state, close the beginning of the lock on the wheel of the normally open input solenoid valve, let the braking force unchanged, if the wheel continues to hold, then open the normally closed output solenoid valve, The braking pressure on this wheel is quickly moved down due to the presence of a straight brake fluid storage tank, which prevents the wheel from being completely held dead due to excessive braking power. In the braking state always at the best point (slip rate S is 20%), the braking effect to achieve the best, the most safe driving.

System structure: brake pedal, brake master cylinder, wheel speed sensor, ECU and hydraulic control unit of electronic control unit.

• What are the strong real-time functional requirements of this system? Which real-time events need to be responded to in real time, and the magnitude of the allowed real-time delay is estimated.

Real-time functional requirements:

1, testing the speed of each wheel

2. Control the liquid pressure in each brake cylinder

Real-time Response events:

1. Does the wheel tend to be held dead

2, whether the speed reaches a certain value (such as 5km/h or 8km/h)

Real-time delay order of magnitude estimation: allowed real-time delay orders of magnitude 0.01s

• If you are a software designer, to implement these real-time functions, design several real-time tasks?

To implement these real-time functions, you need to design 2 real-time tasks: one is to detect the speed of each wheel through a speed sensor, and the other is to control the braking pressure of each brake cylinder by means of a hydraulic solenoid valve.

• What are the time-triggered or event-triggered tasks, and if it is time-triggered, what is the period?

These live tasks are time-triggered and have a period of approximately 10ms.

• Are these real-time tasks independent of each other or are there certain dependencies? Analyze this dependency.

In ABS, a rotational speed sensor is placed on each wheel, and the signal for each wheel speed is input to the electronic control device. The electronic control device monitors and determines the motion status of each wheel according to the input signals of each wheel transducer and forms corresponding control instructions. Therefore, the two real-time tasks have a dependency relationship, that is, the solenoid valve to each brake cylinder braking pressure real-time control to the wheel speed of the real-time detection as the premise.

• Do you need to use some shared hardware resources between these real-time tasks? Lists this dependency.

Both of these real-time tasks are done through the same controller, so share the CPU.

Reference:

Http://baike.sogou.com/v3938011.htm?fromTitle=ABS

Http://www.360doc.com/content/16/1129/13/38614704_610435659.shtml

"Real-time control software Design" first week of work