1、大连交通大学 2012 届本科生毕业设计外文翻译 1 外文原文 Design of PWM Controller in a MCS-51 Compatible MCU Introduction PWM technology is a kind of voltage regulation method by controlling the switch frequency of DC power with fixed voltage to modify the two-end voltage of load.This technology can be used for a variety of
2、 applications including motor control, temperature control and pressure control and so on. In the motor control system shown as Fig. 1, through adjusting the duty cycle of power switch, the speed of motor can be controlled. As shown in Fig. 2, under the control of PWM signal, the average of voltage
3、that controls the speed of motor changes with Duty-cycle ( D = t1/T in this Figure ), thus the motor speed can be increased when motor power turn on, decreased when power turn off. Fig.1: The Relationship Fig.2 Architecture of between Voltage of Armature PWM Module Therefore, the motor speed can be
4、controlled with regularly adjusting the time of turn-on and turn-off. There are three methods could achieve the adjustment of duty cycle: (1) Adjust frequency with fixed pulse-width. (2) Adjust both frequency and pulse-width. (3) Adjust pulse-width with fixed frequency. Active steering control in th
5、e form of secondary yaw control (SYC) and actuated wheelset yaw (AWY)have been in prototype development. This paper presents a new active 大连交通大学 2012 届本科生毕业设计外文翻译 2 steering bogie design, actuated yaw force steering (AY-FS), that is able to steer under high traction loads in tight curves. The AY-FS
6、bogie design is compared with the AWY design. The steering performance AWY under high traction loads has not been previously reported. This paper examines five control methods, three for AWY and two for AY-FS bogies and assesses the traction curving and stability control performance of the alternati
7、ve designs and control methods compared with each other and to passive steering bogie designs.The curving performance results showed considerable advantage in the proposed AY-FS bogies over the AWY. It was shown that control must be applied to both the yaw angle and the steering angle of the bogie t
8、o achieve the best traction steering performance which was not possible with the AWY bogies. The proposed new bogie designs of AY-FS overall give better traction curving and stability performance than the AWY designs. Active suspensions and more recently active steering has received increasing inter
9、est for high-speed train sets 1,2. Active steering control in the form secondary yaw control (SYC) 3 and actuated wheelset yaw (AWY) 4 exist in developments up to prototype stage. SYC bogies control the bogie yaw angle Figure 1 and can improve the wear or creep force saturation at the wheelrail cont
10、act which is the concern for hauling locomotives. However, improvement is limited to the even distribution of wheelset angle of attack and flange contact forces. SYC bogies are more successful in improving stability and reducing track shifting forces on the rail than reducing creep energy. Track shi
11、fting forces become limiting only for high-speed tilting trains. Recent patents have been made for AWY in a three axle bogie 5 including control based on either suspension deflection or gyroscopic inputs. Generally, there are four methods to generate the PWM signals as the following: (1) Generated b
12、y the device composed of separate logic components. This method is the original method which now has been discarded. (2) Generated by software. This method need CPU to continuously operate instructions to control I/O pins for generating PWM output signals, so that CPU can not do anything other. Ther
13、efore, the method also has been discarded gradually. (3) Generated by ASIC. The ASIC makes a decrease of CPU burden and steady work generally has several functions such as over-current protection, dead-time adjustment and so on. Then the method has been widely used in many kinds of occasion now. (4)
14、 Generated by PWM function module of MCU. Through embedding PWM function module in MCU and 大连交通大学 2012 届本科生毕业设计外文翻译 3 initializing the function, PWM pins of MCU can also automatically generate PWM out signals without CPU controlling only when need to change duty-cycle. It is the method that will be
15、implemented in this paper. In this paper, we propose a PWM module embedded in a 8051 microcontroller. The PWM module can support PWM pulse signals by initializing the control register and duty-cycle register with three methods just mentioned above to adjust the duty cycle and several operation modes
16、 to add flexibility for user. The following section explains the architecture of the PWM module and the architectures of basic functional blocks. Section3 describes two operation modes. Experimental and simulation results verifying proper system operation are also shown in that section. Depending on
17、 mode of operation, the PWM module creates one or more pulse-width modulated signals, whose duty ratios can be independently adjusted. Implementation of PWM module in MCU Overview of the PWM module A block diagram of PWM module is shown in Fig.3. It is clearly from the diagram that the whole module
18、is composed of two sections: PWM signal generator and dead-time generator with channel select logic. The PWM function can be started by the user through implementing some instructions for initializing the PWM module. In particular, the following power and motion control applications are supported: DC Motor Uninterruptablel Power Supply (UPS) The PWM module also has the following features: Two PWM signal outputs with complementary or independent operation Hardware dead-time generators for complementary mode Duty cycle updates are configurable to be immediated or synchronized to the PWM
