1、外文翻译步进电机基础附录A 资料翻译A.1 英文资料Stepper Motor BasicsTieluo Lin.Jianxun Zhang DSP-based microstep controller of stepper motorIntelligent Control and Automation, 2004 Fifth World Congress on Volume 5, 15-19 June 2004.A stepper motor is an electromechanical device which converts electrical pulses into discre
2、te mechanical movements. The shaft or spindle of a stepper motor rotates in discrete step increments when electrical command pulses are applied to it in the proper sequence. The motors rotation has several direct relationships to these applied input pulses. The sequence of the applied pulses is dire
3、ctly related to the direction of motor shafts rotation. The speed of the motor shafts rotation is directly related to the frequency of the input pulses and the length of rotation is directly related to the number of input pulses applied.Stepper Motor Advantages and DisadvantagesAdvantages1. The rota
4、tion angle of the motor is proportional to the input pulse.2. The motor has full torque at standstill (if the windings are energized)3. Precise positioning and repeatability of movement since good stepper motors have an accuracy of 3 5% of a step and this error is non cumulative from one step to the
5、 next.4. Excellent response to starting/stopping/reversing.5. Very reliable since there are no contact brushes in the motor. Therefore the life of the motor is simply dependant on the life of the bearing.6. The motors response to digital input pulses provides open-loop control, making the motor simp
6、ler and less costly to control.7. It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to the shaft.8. A wide range of rotational speeds can be realized as the speed is proportional to the frequency of the input pulses.Disadvantages1. Resonances can occu
7、r if not properly controlled.2. Not easy to operate at extremely high speeds.Open Loop OperationOne of the most significant advantages of a stepper motor is its ability to be accurately controlled in an open loop system. Open loop control means no feedback information about position is needed. This
8、type of control eliminates the need for expensive sensing and feedback devices such as optical encoders. Your position is known simply by keeping track of the input step pulses.Stepper Motor TypesThere are three basic stepper motor types. They are : Variable-reluctance Permanent-magnet HybridVariabl
9、e-reluctance (VR)This type of stepper motor has been around for a long time. It is probably the easiest to understand from a structural point of view. Figure 1 shows a cross section of a typical V.R. stepper motor. This type of motor consists of a soft iron multi-toothed rotor and a wound stator. Wh
10、en the stator windings are energized with DC current the poles become magnetized. Rotation occurs when the rotor teeth are attracted to the energized stator poles.Figure 1. Cross-section of a variablereluctance(VR) motor.Permanent Magnet (PM)Often referred to as a “tin can” or “canstock” motor the p
11、ermanent magnet step motor is a low cost and low resolution type motor with typical step angles of 7.5 to 15. (48 24steps/revolution) PM motors as the name implies have permanent magnets added to the motor structure. The rotor no longer has teeth as with the VR motor. Instead the rotor is magnetized
12、 with alternating north and south poles situated in a straight line parallel to the rotor shaft. These magnetized rotor poles provide an increased magnetic flux intensity and because of this the PM motor exhibits improved torque characteristics when compared with the VR type.Hybrid (HB)The hybrid st
13、epper motor is more expensive than the PM stepper motor but provides better performance with respect to step resolution, torque and speed. Typical step angles for the HB stepper motor range from 3.6 to 0.9 (100 400 steps per revolution). The hybrid stepper motor combines the best features of both th
14、e PM and VR type stepper motors. The rotor is multi-toothed like the VR motor and contains an axially magnetized concentric magnet around its shaft. The teeth on the rotor provide an even better path which helps guide the magnetic flux to preferred locations in the airgap. This further increases the
15、 detent, holding and dynamic torque characteristics of the motor when compared with both the VR and PM types.The two most commonly used types of stepper motors are the permanent magnet and the hybrid types. If a designer is not sure which type will best fit his applications requirements he should fi
16、rst evaluate the PM type as it is normally several times less expensive. If not then the hybrid motor may be the right choice.There also excist some special stepper motor designs. One is the disc magnet motor. Here the rotor is designed sa a disc with rare earth magnets, See fig. 5 . This motor type
17、 has some advantages such as very low inertia and a optimized magnetic flow path with no coupling between the two stator windings. These qualities are essential in some applications.Size and PowerIn addition to being classified by their step angle stepper motors are also classified according to fram
18、e sizes which correspond to the diameter of the body of the motor. For instance a size 11 stepper motor has a body diameter of approximately 1.1 inches. Likewise a size 23 stepper motor has a body diameter of 2.3 inches (58 mm), etc. The body length may however, vary from motor to motor within the s
19、ame frame size classification. As a general rule the available torque output from a motor of a particular frame size will increase with increased body length.Power levels for IC-driven stepper motors typically range from below a watt for very small motors up to 10 20 watts for larger motors. The max
20、imum power dissipation level or thermal limits of the motor are seldom clearly stated in the motor manufacturersdata. To determine this we must apply the relationship P=VI For example, a size 23 step motor may be rated at 6V and 1A per phase. Therefore, with two phases energizedthe motor has a rated
21、 power dissipation of 12 watts. It is normal practice to rate a stepper motor at the power dissipation level where the motor case rises 65C above the ambient in still air. Therefore, if the motor can be mounted to a heatsink it is often possible to increase the allowable power dissipation level. Thi
22、s is important as the motor is designed to be and should be used at its maximum power dissipation ,to be efficient froma size/output power/cost point of view.When to Use a StepperMotorA stepper motor can be a good choice henever controlled movement is equired. They can be used to advantage in applic
23、ations where you need to control rotation angle, speed, position and synchronism. Because of the inherent advantages listed previously, stepper motors have found their place in many different applications. Some of these include printers, plotters, highend office equipment, hard disk drives, medical
24、equipment, fax machines, automotive and many more.The Rotating Magnetic FieldWhen a phase winding of a stepper motor is energized with current a magnetic flux is developed in the stator. The d When a phase winding of a stepper motor is energized with current a magnetic flux is developed irection of
25、this flux is determined by the “Right HandRule” which states: “If the coil is grasped in the right hand with the fingers pointing in the direction of the current in the winding (the thumb is extended at a 90 angleto the fingers), then the thumb will point in the direction of the magnetic field.”Figu
26、re 2 shows the magnetic flux path developed when phase B is energized with winding current in the direction shown. The rotor then aligns itself so that the flux opposition is minimized. In this case the motor would rotate clockwise so that its south pole aligns with the north pole of the stator B at
27、 position 2 and its north pole aligns with the south pole of stator B at position 6. To get the motor to rotate we can now see that we must provide a sequence of energizing the stator windings in such a fashion that provides a rotating magnetic flux field which the rotor follows due to magnetic attr
28、action.Figure 2 Magnetic flux path through a two-pole stepper motor with a lag between the rotor and stator.Torque GenerationThe torque produced by a stepper motor depends on several factors. The step rate The drive current in the windings The drive design or typeIn a stepper motor a torque is devel
29、oped when the magnetic fluxes of the rotor and stator are displaced from each other. The stator is made up of a high permeability magnetic material. The presence of this high permeability material causes the magnetic flux to be confined for the most part to the paths defined by the stator structure
30、in the same fashion that currents are confined to the conductors of an electronic circuit. This serves to concentrate the flux at the stator poles. The torque output produced by the motor is proportional to the intensity of the magnetic flux generated when the winding is energized.The basic relation
31、ship which defines the intensity of the magneticflux is defined by:H = (N i) l where:N = The number of winding turnsi = currentH = Magnetic field intensityl = Magnetic flux path lengthThis relationship shows that the magnetic flux intensity and consequently the torque is proportional to the number o
32、f winding turns and the current and inversely proportional to the length of the magnetic flux path. From this basic relationship one can see that the same frame size stepper motor could have very different torque output capabilities simply by changing the winding parameters. More detailed information on how the winding parameters affect the output capability of the motor can be found in the application note entitled “DriveCircuit Basics”.Stepping ModesThe following are the most common drive modes. Wave Drive (1 phase on) Fu
