Månadsvis arkiv: augusti 2016
Servo motor is an engine that controls the operation of mechanical components in the servo system.Servo motor can make the control speed, position accuracy is very accurate, can be converted to torque and speed voltage signals to drive the control object. Servo motor rotor speed by the control signal input, and can respond quickly, in automatic control system that is used for the implementation of components, and has small electromechanical time constant, high linearity, initiating voltage characteristics, the received signal is converted into the motor shaft angular velocity or displacement output. DC and AC yaskawa servo motor is divided into two major categories, the main feature is that when the signal voltage is zero without rotation, speed with the increase of torque and uniform decline.
Telling a servo motor to move to specific angle is easily accomplished using write(). The Arduino will do all the nessary caculation;determining the length of the pulse to generate and sending the pulse on time:
The angle parameter is an integer number,from 0 to 180, and represents the angle in degrees.
If you require precision, you can specify the length of the pulse by using the writeMicroseconds () function. This eliminates the need for calcuation by the Arduino and specifies the exact pulse length, an integer, expressed in microsenconds:
servo.write Microseconds (microseconds);
It does not matter what the original position waw, the servo motor ASD-B2-0421-B automatically adjusts its position. The Arduino does not need to calculate this either; all the intelligence is embedded inside the motor assembly. It does, however, keep the last angle that it was instructed to use, and this value can be feched with read();
int angle * servo.read()
Remember that servo motors can receive only instructions and not return information. The value returened by read() is the value inside the Arduino. When connecting a servo motor, there is no way to know what position it was in initially. It can be helpful to set a servo motor to a default position before starting your application. (For exapmle, a remote-controlled car should probably have the wheels turn so that they are at 90 degrees; withoust adjusting the steering, the owner would expect the car to go straight and not at an angle.)
Servo motors and other physical objects take time to get to where you want them to be, so it’s considered good practice to give your motor a bit of time to get where it wants to go. Some motors move faster than others, if you’re unsure of how much time you’ll need, it’s best to check your motor’s documentation.
There are four basic types of gear reducers on the market today:helical gears,parellel shaft helical gears,helical bevel gears,and helical worm gears. The latter three types of gear reducers are often used in the theatre industry. Both parallel shaft and helical bevel Gear reduction motors are very efficient in transmittting power from the motor to the output shaft. The helical worm gear reducer is inefficient in its transmission of power from the motor to the output shaft. The helical worm design is the mostly widely used gear reducer type, offering long service life overload and shock tolerance.
Efficient gear reducers are used on most of today’s packaged winch systems. They are also used on most fire curtain motor systems as they are easy to back drive, which is the reverse of the normal operation. The output shaft is used to turn the input shaft. Many fire curtain release systems release the brake on the motor, using the weight of the fire curtain to turn the output shaft of the gear reducer, which turns the motor. A hydraulic dampener attached to the motor controls the descent speed of the fire curtain.
An inefficient gear reducer design does, however, have advantages in the threatre world. A helical worm gear reducer with a gear ratio greater than 60:1 statistically cannot be back-driven. This means that a load on the output shaft will remain staionary even if the motor brake is released. Most line shaft, drum, and counterweight assist winches use this type of planetary gear reducer because of this feature. Helical worm gear reducers are a simple design that is very cost-effective to produce. This design lends itself to the lower output RPM and higher gear ratios used in the theatre industry.
Gear reducers are filled with oil and are vented because the oil will expand as the reducer is used. The oil helps to keep the reducer cool. The reducer will have breather vent and a drain plug. While it may look like as if they can be mounted or oriented in any position, it is very important to be certain that the vent is at the top and drain at the bottom when the reducer is mounted in its final position. The amount of oil with which the reducer is filled varies with the orientation that is used. The orientation is also important regarding the bearings that are installed into the reducer. The manufacturer will install different bearing depending on whether the bearing is below or above the oil level in the reducer. Thus it is important to order a gear reducer for the specific orientation for which it will be used.
Gear reducers also have their own service factor, which is defined by the American Gear Manufactures Association (AGMA). AGMA adjusts a reducer’s ratings relative to the individual load charateristics of the reducer. AGMA’s ratings are based upon time duration. For winches used for between three and ten hous per day the service factor is 1.25. For winches used for more than ten hours per day the service factor is 1.5.
Numerous industrial machines need energy at slow speeds and higher torque. Conveyors and concrete mixers are typcial examples of machinery with such specifications. At speeds of 780 rpm and much less, the following drives might be prudently utilized: chain drive, belt drive, separate speed reducer coupled towards the motor, or gear motor.
The gear reducer motor is really a speed-reducing motor that provides a direct energy drive from a single unit. The gear motor offers an very compact, effective, packaged energy drive. A gear motor generally consists of a standdard AC or DC motor along with a sealed gear train properly engineered for the load. This assembly is mounted on a single base as a 1 package, enclosed pwoer drive. The benefit of this unit is its intense compactness. A gear motor really is smaller sized than a low-speed regular motor from the exact same horsepower.
The motor-shaft pinion of the worm gear motor drives the gear or series of gears in an oil bath that is linked with the output shaft. This type of arrangement is usually the most economical and convenient way to obtain low speeds of approximately 1 rpm to 780 rpm.
One-unit gear motors are available with the following options:(1)shafts parallet to each other or at right angls, (2) polyphase, single-phase, or DC voltages, and (3) horsepower ratings ranging from approximately 1/6 hp to 200 hp.
Gear motor are accessible in numerous from the regular motor kinds like squirrel cage or wound rotor induction motors, operating at either continuous or adjustable speeds. The manage gear for the motor is chosen exactly the same as for any other motor from the exact same kind.
When choosing a gear motor, an essential consideration will be the degree of gear service and gear life primarily based around the load circumstances to which the motor will probably be subjected. Gear motors are divided into 3 classes. Every class utilizes various gear sizes to deal with particular load circumstances. Every class give concerning the exact same life for the gears. The American Gear Manufactures’s Assocation has defined 3 operationg conditons generally discovered in industrial service and has established 3 regular gear classifications to meet these circumstances.
Class I: For steady loads within the motor rating of 8 hours per day duration, or for intermittent operation under moderate shock conditions.
Class II: For 24-hour operation at steady loads within the motor rating, or 8-hour operation under moderate shock conditions.
Class III: For 24-hour operation under moderate shock conditions, or 8-hour operation under heavy shock conditions.
For conditions that are more severe than those covered by Class III gears, a fluid drive unit may be incorporated in the assembly to cushion the shock to an acceptable value.
To achieve multiple speeds, separate units are available with a transmission comparable to that of an automobile. These units must be assembled with the motor and the driven machine. Because the amount of power lost in gearing is very small, the multiple drive has essentially constant horsepower. In other words, as the output speed is decreased, the torque is increased. Generally, this means that larger shaft sizes are needed for the output side.
A worm gear assembly resembles a single threaded screw that turns a modified spur gear with slightly angled and curved teeth. Worm Gear reduction motors may be fitted with either a right-, left-hand, or hollow output (drive) shaft. This correct angle gearing kind is utilized when a sizable speed reduction or perhaps a big torque improve is needed inside a restricted quantity of space. Figure 1 shows a single thread (or single begin) worm along with a forty tooth worm gear resulting inside a 40:1 ratio. The ratio is equal towards the quantity of gear teeth divided by the amount of starts/threads around the worm. A comparable spur gear set having a ratio of 40:1 would need a minimum of two stages of gearing. Worm gears can attain ratios of much more than 300:1.
Worm gears have an inherent design advantage over other gear sets; the worm can easily turn the dc worm gear motor, but the gear cannot turn the worm. In lifting applications, this feature acts as a secondary brake due to limited back drivability.
Worms can be made with multiple threads/starts as shown in Figure 2. The pitch of the thread remains constant while the lead of the thread increases. In these examples, the ratios relate to 40:1, 20:1, and 13.333:1 respectively.
Worm gear sets can be self-locking: the worm can drive the gear, but due to the inherent friction the gear cannot turn (back-drive) the worm. Typically only in ratios above 30:1. This self-locking action is reduced with wear, and should never be used as the primary braking mechanism of the application.
27RPM DC24V 2.45NM 25kg.cm Turbo Worm Gear Motor GW31ZY DIY Robot
1.Every product has a unique Manufacturing Part Number label on the inner package that proves it has been qualified,which include Part Number,Model Number and inspection date information;
2.If you have any questions about the item,please provide us the Manufacturing Part Number for checking,your profits will be guaranteed.
3.Use for labeling machines, remote control curtains, automatic voltage electricity, grills, ovens, washing machines, garbage disposal machines, household appliances, slot machines, the banknote recognition, automatic actuator, coffee machine, towel disposal, lighting, etc.
4.Low speed structure,high power,large output torque,stable performance,small installation space and self lock,etc.
5.This type is low speed Worm Gear DC Motor,self locking.
6.Widely used in various of occasions that require special install size.
The worm gear is usually bronze and the worm is steel, or hardened steel. The bronze component is designed to wear out before the worm because it is easier to replace.
The hoist motor can transmit motion through the gear reducer, but the load cannot transmit motion back through the gear reducer.
Regulates the lowering speed of the load
The load will not be allowed to free fall
OSHA [1910.179] recognizes this as an approved means of controlled braking
In an industry where ‘load brakes’ and ‘regenerative braking’ are widely accepted, Electrolift offers the better option by using a worm drive gearbox as the secondary braking function.
The main advantages of Electrolift’s non-load brake worm drive gear reducer:
Constant load on the load block. Load brake hoists are prohibited from doing this because it does not allow the load brake to release causing overheating and premature failure.
Long lifts – Long lifts cause load brakes to overheat and prematurely fail
Faster lifting speeds – Load brakes accumulate excessive heat as lifting speeds increase.
Inherently safe – Worm drives do not need controls or high maintenance mechanisms to ensure safe lifts.
Low Maintenance – Less moving parts than gearboxes that require complex load brake mechanisms
Stepper motors can be used in various areas of your microcontroller projects such as making robots, robotic arm, automatic door lock system etc. This tutorial will explain you construction of Nema 42 stepper motor (unipolar and bipolar stepper motors ), basic pricipal, different controlling types (Half step and Full step), Interfacing Techniques (using L293D or ULN2003) and programming your microcontroller in C and assembly to control stepper motor.
Types of Stepper Motors
There are basic two types of stepper motors available in market.
Unipolar stepper motor
The unipolar stepper motor has five or six wires and four coils (actually two coils divided by center connections on each coil). The center connections of the coils are tied together and used as the power connection. They are called unipolar steppers because power always comes in on this one pole.
Bipolar stepper motor
The bipolar Linear Stepper Motor usually has four wires coming out of it. Unlike unipolar steppers, bipolar steppers have no common center connection. They have two independent sets of coils instead. You can distinguish them from unipolar steppers by measuring the resistance between the wires. You should find two pairs of wires with equal resistance. If you’ve got the leads of your meter connected to two wires that are not connected (i.e. not attached to the same coil), you should see infinite resistance (or no continuity).
As already said, we will talk mostly on ”Unipolar stepper motors” which is most common type of stepper motor available in the market.A simple example of 6 lead step motor is given below and in 5 lead step motor wire 5 and 6 are joined together to make 1 wire as common.
Unipolar versus bipolar stepper motor interface
There are three common types of stepper motor interfacing: universal, unipolar, and bipolar. They can be identified by the number of connections to the motor. A universal stepper motor has eight, while the unipolar has six and the bipolar has four. The universal stepper motor can be configured for all three modes, while the unipolar can be either unipolar or bipolar. Obviously the bipolar cannot be configured for universal nor unipolar mode. Table 17-7 shows selected stepper motor characteristics. Figure 17-10 shows the basic internal connections of all three type of configurations.
Unipolar stepper motors can be controlled using the basic interfacing shown in Figure 17-11, whereas the bipolar stepper requires H-Bridge circuitry. Bipolar stepper motors require a higher operational current than the unipolar; the advantage of this is a higher holding torque.
The diagram below shows the interfacing of stepper motor to a micro-controller. This is general diagram and can be applied to any micro-controller family like PIC micro-controller, AVR or 8051 micro-controller.
Since, the micro-controller cannot provide enough current to run the motor, a driver like a ULN2003 is used to drive the motor. Similarly, individual transistors or any other driver IC can also be used to drive the motor. See to it that if required, the external pull up resistors is connected to pins depending on the micro-controller you use. The motor must never be directly connected to the controller pins. The motor Voltage depends on the size of the motor. A typical 4 phase uni-polar stepper motor has 5 terminals. 4 phase terminals and one common terminal of the center tap that is connected to ground.
The programming algorithm for continuous rotation in clockwise mode is given below:
Initialize the port pins used for the motor as outputs
Write a common delay program of say 500 ms
Output first sequence-0 × 09 on the pins
Call delay function
Output second sequence-0 × 0 c on the pins
Call delay function
Output third sequence-0 × 06 on the pins
Call delay function
Output fourth sequence-0 × 03 on the pins
Call delay function
Go to step 3
Before the closed-loop system can be simulated it is necessary to choose appropriate values for yaskawa servo motors and load parameters. Every set of parameter values will, of course, lead to a unique simulation result, but in this paper it is only possible to present results corresponding to a single set of values. Some typical set of parameter values must therefore be selected.
A type 23HS-108 motor was chosen for the simulations because it typifies small hybrid Nema 23 stepper motor. The stator windings are assumed to be excited by a 24 V, 2 A bipolar chopper drive.
Choice of the load parameters is more difficult because there really is no typical load. As a general rule, however, the load inertia will not normally greatly exceed the motor inertia and for the purpose of these simulations the total inertia will be assumed to be equal to the motor inertia. Coulomb and viscous friction in the load usually dominate the motor friction. Up to a point the performance of the closed-loop system described here improves with increasing friction because friction provides the only significant damping of overshoot. The worst-case assumption is that the load friction is zero, and in the simulations presented here the total friction is assumed to be equal to the motor friction. In any real system the overshoot is likely to be less serious than that predicted by the simulations.
The results of the simulations are displayed in graphical form with the rotor angular velocity dmpos/dt (expressed in steps/s) plotted against positional error mpos-cpos (expressed in steps). There are three important situations to consider, all of which may lead to loss of synchronization in open-loop systems: operation at a resonant rate, operation above the maximum start-stop (pull-in) rate and excessive load torque.
Loss of synchronization due to resonance is only observed in lightly damped systems, particularly if an 8-step sequence is used. Figure 3 shows the response of open-loop and closed-loop systems to a sequence of 20 steps at the resonant rate of 153 steps/s. Both systems start from rest with zero positional error. In the case of the open-loop system the positional error builds up over several steps until at the 6th step the error exceeds 4 steps and synchronization is lost. This does not happen in the closed-loop system where, in spite of oscillations of approximate amplitude ±4 steps around the command position, synchronization is maintained.
The effect of operating outside the pull-in characteristic of the motor is shown in figure 4 where a
sequence of 100 steps at a rate of 4000 steps/s is applied to a motor initially at rest. As expected this simulation demonstrates that the open-loop system loses synchronization whereas the closed-loop system settles down to a rotor velocity around 4000 steps/s, and at the end of the step sequence returns to the zero error position.
Finally, figure 5 shows the effect of applying a torque of 0.5 N (which exceeds the peak motor torque) for 10 ms. This causes rapid loss of synchronization in the open-loop system whilst the closed-loop system recovers, even from very large positional errors.
Ideally the recovery from positional error should be asymptotic (that is free from overshoot) but this is far from being the case as can be seen from figures 4 and 5. The control system itself provides no damping and correct operation relies on friction in the motor and load, and on electrical damping provided by the sequencer. In most applications load friction will provide a more rapid approach to rest than that illustrated.
It is probable that a more sophisticated control algorithm could be devised which generated additional damping. For example, the motor speed could be sensed and used in a manner similar to the tachometer in a conventional servomechanism. Unfortunately this would detract from the essential simplicity of the control algorithm described here, and would involve adjustments to suit particular motor/load combinations.