Some controller/drive systems can commutate highpole step motors to form ac brushless a perfect motion system, a motor turns a certain predetermined amount for every unit of electricity it is given. But if the load on the motor becomes too big, it doesn't matter how much power you try to feed it. Beyond a certain limit — maximum torque rating — motors can no longer turn. Motions become erratic, severely compromising accuracy. Why? Servo systems pick up on the resulting error right away, but open-loop systems don't. This is most troublesome when it appears in systems with stepping drive technology. Stepper systems are designed to provide position control without expensive feedback where precise motion is a requirement. Exceeding the available torque or other limits causes lost steps — failures to advance in position that go undetected. As in the below half-stepping produces eight steps per electrical rotation — every 45°— while microstepping ranges from 16 steps per revolution to hundreds or even thousands of points around each electrical rotation. To move the motor, currents to the stator phase windings are varied so as to produce a rotating magnetic field. The rotor attempts to align itself with the magnetic field, following the rotation and producing motion. The high pole count of most stepper motors — 100 poles for a common stepper motor — requires 50 full electrical rotations of the phase currents for one rotor rotation. The phase currents are driven with a sine-cosine signal approximation; that is, one phase is driven with an approximation of a sine wave while the other is driven with an approximation of a cosine signal. When full-stepping a motor, there are four full steps per electrical rotation. These may be located either at 0, 90, 180, and 270° in the case of wave stepping when one phase is on or at 45, 135, 225, and 315° with two-phases-on stepping. Half-stepping produces eight steps per electrical rotation — every 45° — while microstepping ranges from 16 steps per revolution to hundreds or even thousands of points on each electrical rotation. In fact, as we'll discuss further, this is the capability on which “hybrid stepper” solutions to lost steps are based. A hybrid stepper motor is actually a high pole count ac synchronous permanent-magnet motor that may be operated down to zero frequency. Resonance problems A motor produces torque only when its rotor is not aligned with the stator magnetic field. Torque varies in a roughly sinusoidal manner with this “error angle.” Two things in a motor combine to effectively form a non-linear spring/mass rotary pendulum • The interaction between the stepper motor stator field and the rotor. • The rotor's moment of inertia. Each step or fractional step applied to the motor windings shifts the equilibrium point of the pendulum, establishing a new error angle. The new error angle results in a new torque point, and the rotor — operating as a spring/mass rotary pendulum — attempts to follow. If the system is lightly damped which is common and the system is given enough time, the rotor overshoots the equilibrium point, ringing back and forth until it settles in. If the next step occurs when the system has sufficient speed while going in the opposite direction, then the peak instantaneous torque available may not be sufficient to keep the rotor within ±180 electrical degrees. When this occurs, the system slips into the adjacent cycle of the error-torque sine wave. When this happens the stepper, in effect, has just lost four steps. If the rotor is not able to regain synchronization with the stator, many more steps may be lost. The motor produces torque only when the rotor is not aligned with the stator magnetic field, varying in a roughly sinusoidal manner with error angle. A rotor's ringing as a rotary pendulum — associated with dips in torque available from an open-loop stepper — is commonly called low-frequency resonance. The motor, applied current, and load all affect this resonant frequency, resulting in low-frequency resonance usually around 50 to 150 rpm, corresponding roughly to 150 to 500 steps per sec. Stepper correction Microstepping reduces the amplitude of the torque variations between steps, which reduces the excitation of the pendulum resonance, and thus the likelihood that the error angle will get large enough to lose steps. Note microstepping is most effective with motors that have been optimized for it. To illustrate, many stepper motors optimized for full stepping have a detent torque that aids full-step positions, but actually causes significant cogging when microstepping. The resolution of microstepping drivers often drops as the rotational speed increases; the reduction in resolution is inevitable due to the limited bandwidth of both controller and driver. For argument's sake, imagine a designer attempted to operate a microstepping controller with 40,000 steps per sec at 50 rps 3,000 rpm. It would then have to output 2,000,000 microsteps per sec to keep all the steps. Even if this were possible, a typical PWM driver only operates at 20 to 40 kHz — so the fine interpolations would never reach the motor. To address this inability to hit every microstep at higher speeds, the number of microsteps per second is often reduced as the motor speed increases. Transitions between these different resolutions can cause an impulse in torque to the motor, causing ringing that can result in lost steps. Instability There is another torque reduction that takes place at higher speeds, roughly corresponding to the speed at which the power-supply/driver combination becomes unable to control the current. This, in turn, corresponds to the start of the parabolic “constant power” portion of the torque curve, called mid-resonance instability. Loss of the ability to control current occurs when a motor's back-EMF rises to the point where power-supply voltage applied to the driver cannot overcome both the back-EMF and resistive and inductive drops at the requested current. The current undergoes a 90° phase lag from the commanded current as the driver switches from current control mode to voltage drive mode. Any mechanical ringing of the rotor pendulum causes the motor to speed up and slow down, changing both the velocity and relative angle between the driven field angle and the rotor angle. This changes two things the magnitude and angle of the back EMF with respect to the phase of the commanded current. Why does this matter? It can cause the driver to switch back and forth between voltage mode full on and current mode chopping. This can reduce the damping of the system, or even pump up the ringing until the rotor loses sync with the commanded position and loses steps, or stops spinning altogether. Operation in this speed region may require either mechanical damping or electrical damping to stabilize the operation of the motor to provide usable torque. Sudden movements, external forces Low-frequency resonance and mid-frequency instability are not the only ways to lose steps. The rotary pendulum is also set into swinging in other words, becomes excited by sudden changes in commanded velocity and load. Instabilities can also be mechanical. Shafts, couplings, and power transmission components between motor and load also act as rotary springs. For example, gear trains release the load when changing direction, due to backlash. While the load is uncoupled from the system, the motor accelerates because of lower inertia until the backlash has been taken up. When the gears engage again, the difference in velocity between the motor and load can reflect excess torque back to the motor. Thus the system cycles The motor slows below the speed of the load, again the load decouples, and then the motor speeds up. In some cases, the change in speed may be enough for the gears to first strike on one face and then rebound and strike on the opposite side, to repeat several times. The exact timing of the reversal ringing may vary with both the position of the gear train and with the wear of the gears, making it difficult to choose a stepping sequence that compensates. A different stability issue arises with belt-driven linear movers. These units experience a resonance, the frequency of which constantly changes. As anyone who has ever played a stringed instrument or a rubber band stretched across a cup can attest, pitch or resonant frequency can be varied by changing either the string's tension or its length. The motion of a linear belt mechanism varies both of these. Linear force applied to the carrier and its load is the difference between the tensions of the two belt halves, while the position of the carrier varies the length of these belt sections. Note that these same effects change both the resonance frequency of the belt itself, and that of the belt-load system. This means that the same move with the same load and motor may work fine with the system starting at position A but not at position B. And what if the system carries a varying load? That only complicates the matter further. Increasing stability Both mechanical and electrical approaches are used to stabilize stepper motors. Mechanical approaches usually involve increasing motor rotary inertia to make load variations less significant, or adding damping to the system. Rotary inertia is increased either by swapping out the motor size or design, or by coupling flywheels to the motor shaft as close to the motor as possible. A system's mechanical damping is increased by including magnetic dampers, viscous inertial dampers, ferrofluid, and elastic motor mounts, couplers, and belts. On the other hand, electronic approaches to increase stability typically measure directly or indirectly motor position and speed. Then current to motor windings is varied in a way that damps the system. These electronic methods include • Measuring or estimating the back EMF of each winding which includes both speed and position information and adding a portion of the back EMF signal into the commanded current at each winding • Modifying driver circuits • Using position/velocity information to modify the applied pulse train to the stepper motor • Full servo control of the stepper motor. More resources — for further reading Leenhouts, Albert. Step Motor Design Handbook. Kingman Litchfield Engineering Co., 1990. Labriola, Don and Dan Jones. “Using Magnetic Gearing Performance from a Compact Integrated Servo.” Proc. of 28th Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1999. Houda, Akihiko. “2-Phase Hybrid Stepping Motor with Keep-in-Step Control.” 28th Incremental Motion Control Systems & Devices.” Proc. of 28th Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1999. Rusu, Calin. “DSP Based Control For the Hybrid Stepper Motor with Field Oriented.” Proc. of 28th Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1999. Leenhouts, Albert. “Step Motors and Gear Play.” Proc. of 29th Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1998. Nordquist, Jack. “Origins and Remedies for Resonant Activities in Step Motor Systems.” Proc. of 26th Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1997. Raj, K., B. Moskowitz, J. Torres, D. Cooper, T. Burke, B. Trudeau. “Performance Characteristics of Ferrofluid Steppers.” Proc. of 23th Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1994. Marushima, K. and Ralph Horber. “Development of a High Performance Sensorimotor with Sensor and Driving Coils.” Proc. of 23th Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1994. Ohm, Dal, and Venkatesh Chava. “Torsional Resonance in Servo Systems and Digital Filters.” Proc. of 23th Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1994. Kruse, David. “BLDC/Stepper Motor Controller for High Performance Incremental Motion.” Proc. of 22nd Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1993. Bodson, Marc, John Chiasson, and Ronald Rekowski. “A State Feedback Tracking Controller for a Permanent Magnet Stepper Motor.” Proc. of 21st Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1992. Jufer, Marcel, and G. Heine. “Hybrid Stepping Motors — 25 Years of Development.” Proc. of 25th Incremental Motion Control Systems and Devices. Lebanon IMCSS, 1996.
Footstep sebelah kiri bengkok lantaran jatuh karena jalanan licin. Di momen ini seolah batin saya dan batinnya si Grand saling klik. Layaknya seorang yang sedang jatuh cinta, saya semakin tergila-gila untuk selalu bersamanya. Saat kelas 1 SMP, saya diberi tanggung jawab sepenuhnya untuk merawat motor ini. STNK saya yang pegang.
By Nippon Pulse America Have you ever picked up a motor and discovered it had a few more wires then you were expecting? If so, it was likely a step motor. Step motors are commonly used in a number of products, from wrist watches to printers, IV pumps to gas pumps. They are also found in machine tools, process control systems, tape and disk drive systems, and programmable controllers. Common permanent-magnet PM step motors are the Tin Can or claw-tooth type. They operate on the reaction between a permanent-magnet rotor and an electromagnetic field. As common as step motors are, however, there is much confusion about the differences between Unipolar and Bipolar step motors, and how Constant Current and Constant Voltage step motor drives work. This 2-part series will cover the most important steps of troubleshooting any step motor system. It will include an overview of step motors — what they are and how they work, and how to troubleshoot them. The second article will also cover the electronics needed to make a step motor run, and provide more information on troubleshooting. The basics A step or stepping motor converts electronic pulses into mechanical movement. Each electronic pulse “step” causes the shaft to rotate a certain number of degrees step angle. Thus, a step motor can operate in an open loop application where it will move a certain distance at a certain speed without the need for feedback. The step motor can maintain the holding torque indefinitely when the rotor is stopped without burning up the motor windings. When a step motor has a steady dc signal applied to one stator winding, the rotor will overcome the residual torque and line up with that stator field. The holding torque is the amount of torque required to move the rotor one full step with the stator energized. A step motor converts electronic pulses into mechanical movement. Each pulse “step” causes the shaft to rotate a certain number of degrees step angle, enabling open loop operation. When no power is applied to the windings, a small magnetic force develops between the permanent magnet and the stator. This magnetic force is called the residual, or detent torque. It can be noticed by turning a step motor by hand and is generally about one-tenth of the holding torque. In a typical one-phase step sequence for a two phase motor, phase A of a two-phase stator is energized Step 1. This magnetically locks the rotor in the position shown, because unlike poles attract. When phase A is turned off and phase B is turned on, the rotor rotates 90° clockwise. In Step 3, phase B is turned off and phase A is turned on but with the polarity reversed from Step 1. This causes another 90° rotation. In Step 4, phase A is turned off and phase B is turned on, with polarity reversed from Step 2. Repeating this sequence causes the rotor to rotate clockwise in 90° steps. Here is a typical step sequence for a two phase motor. There are three main types of step motors permanent-magnet PM, variable reluctance VR and hybrid. The permanent-magnet PM step motor operates on the reaction between a permanent-magnet rotor and an electromagnetic field. One of the most common PM motors are the Tin Can or claw-tooth type. In tin can steppers, the rotor shaft is surrounded by a magnet with radially opposing poles. It has no teeth. The stator is a series of poles with wound wire coils. Because of the magnet, the rotor will resist movement even when the motor is not energized. Permanent magnet step motors are used in low-cost, low-power applications. The bill feeder inside vending machines is driven by a permanent magnet step motor. The variable-reluctance VR step motor differs from the PM stepper in that it has no permanent-magnet rotor and no residual torque to hold the rotor at one position when turned off. This type of motor operates on the principle of minimizing the reluctance along the path of the applied magnetic field. One of the first uses for variable-reluctance step motors was to move the direction indicator of torpedo tubes and guns on British warships in the 1920’s. Shortly thereafter, they were used by the US Navy for a similar purpose. The hybrid step motor consists of two pieces of soft iron, as well as an axially magnetized, round rotor. It’s called a hybrid because the motor operates under the combined principles of the permanent magnet and variable-reluctance step motors. The stator core structure of a hybrid motor is essentially the same as its VR counterpart. The main difference is that in the VR motor, only one of the two coils of one phase is wound on one pole, while a typical hybrid motor will have coils of two different phases wound on the same pole. In this cross section of a two-phase hybrid motor, each pole is covered with uniformly spaced teeth that are misaligned with each other by a half-tooth pitch. The interaction of the magnetic field of the permanent magnet and the magnetic field produced by the stator create torque. The two coils at a pole are wound in a configuration known as a bifilar connection. Each pole of a hybrid motor is covered with uniformly spaced teeth made of soft steel. The teeth on the two sections of each pole are misaligned with each other by a half-tooth pitch. Torque is created in the hybrid motor by the interaction of the magnetic field of the permanent magnet and the magnetic field produced by the stator. Most hybrid steppers are NEMA size motors. The windings for steppers come in two types Bipolar and Unipolar. There are a number of advantages to each type of winding. The two-phase stepping sequence described earlier uses a “bipolar coil winding.” Each phase consists of a single winding. It is referred to as a bipolar winding because the current flow on the coils is reversed. By reversing the current in the windings, electromagnetic polarity is reversed. The unipolar winding is sometimes called a four-phase stepper. It consists of two windings on a pole connected in such a way that when one winding is energized a magnetic north pole is created; when the other winding is energized, a south pole is created. It is referred to as a unipolar because the electrical polarity, or current flow, from the drive to the coils is never reversed. What can go wrong with step motors In general, there are four things that can go wrong with a motor They burn up, the brushes go bad, the bearings go bad, or a technician breaks them. They burn up. An important characteristic of the step motor is that it can maintain the holding torque indefinitely when the rotor is stopped. If a step motor stalls out, it is unlikely that it will burn up as with most ac and dc motors. If the motor does burn up it indicates a driver problem. We will explore why this is the case in the next article. Just replacing the motor will cause the motor to burn up again. This is not a common problem with step motors unless there is a bad driver. Example of a bipolar winding and example of a unipolar winding. In a bipolar winding the current flow on the coils is reversed, which reverses electromagnetic polarity. In a unipolar winding, the electrical polarity, or current flow, is never reversed, hence the name unipolar. The brushes go bad. There are no brushes in a stepper motor. Therefore, this will never be a cause of failure. The bearings go bad. The cooler the motor stays, the longer the bearings will last. At times, however, the bearings will go bad. Still, this is not a common problem. The bearings in most inexpensive motors are rated at 3000 hours or more, and most high-end quality motors are rated at 90,000 to 100,000 hours. The technician breaks them. This is the most common cause of failure for step motors. When working with these devices, be careful with them. They do not need to be handled like fine china but don’t try to fix one with a hammer. Most inexpensive motors use glue to hold the shaft to the rotor, and most quality steppers will use grooving along with adhesive. To test the motor, first use an ohmmeter. It will indicate if a winding is burnt up and what type of step motor you have, usually a bipolar or unipolar. A bipolar will always have four leads. A unipolar will have five or six leads. If five leads, the two common wires are connected. A few motors will have eight leads; these motors can be wired as either unipolar or bipolar. Using the ohmmeter, check the resistance of the windings. On a bipolar the resistance for both windings should be the same in both directions. In a unipolar winding, the resistance from each phase to com should be the same in both directions. After you have checked the motor with the ohmmeter, you can use a 9V battery to step the motor through its paces. This will confirm the motor windings are good. You can use the charts in Figure 9 for assistance. You can turn the motor by hand while listening for bad bearings. All PM and hybrid step motors will have some detent torque. PM will have more than the hybrid steppers. If the leads of the step motor are touching, the detent torque will be greatly exaggerated. Be careful! Some technicians have falsely linked this to bad bearings. If the bearings are bad, there will usually be extra axial play in the motor. If possible, check against a known good motor. When replacing a motor, many wonder about the color code for the wires. Remember the windings make up an electromagnet. As long as you have the windings grouped correctly Phase 1 and 3 together and Phase 2 and 4 together the worst that will happen when you go to run the motor is that it will run backwards. To correct, just swap one set of phases 1 and 3 or 2 and 4. A few step motors will have eight leads; these motors can be wired as either unipolar or bipolar. Next time we will explore the differences between Bipolar vs. Unipolar windings and how Constant Current and Constant Voltage types of stepper motor drives work. And answer the question, why do I use a 5V motor when I have a 24V supply? DW Nippon Pulse America You may also like Filed Under Motion control • motor controls, Motors • stepperTagged With nipponpulse
Kataforumer tu dia minum air daun bunga raya merah yang ada 5 kelopak tapi kakak ipar aku punya daun raya bukan yang jenis 5 kelopak, yang jenis berkelopak-kelopak macam bunga ros tu tapi tak apalah, cuba sajalah dulu! Hari ni aku dah cuba minum air daun bunga raya yang warna putih. Aku nak tengoklah macamana period aku bulan ni. Tak salah mencubakan
Sebagai penopang dari bobot motor dan ban, pelek motor merupakan salah satu komponen yang berpengaruh besar pada pengendalian jika bermasalah. Pentingnya pelek motor ini juga karena berhubungan dengan keselamatan dan kenyamanan yang biasa terjadi pada pelek motor adalah kerusakan seperti bengkok atau peyang. Hal ini bisa disebabkan karena ada benturan yang keras dengan permukaan jalan atau objek lain, sehingga konstruksi pelek pelek jari-jari, bukan hal yang sulit untuk memperbaikinya. Cukup melakukan penyetelan dan pengencangan jari-jari, masalah pun selesai. Tapi ketika bentuk pelek jari-jari sudah terlipat, semisal akibat tabrakan keras, sebaiknya diganti baru ketimbang diperbaiki. Lalu bagaimana dengan pelek aluminium atau racing jika terjadi masalah seperti itu? Terlebih, biasanya pelek racing menggunakan material alloy yang keras dan tidak mudah Juga Tips Memilih Pelek Aftermarket Utuk MotorUntuk pelek motor jenis aluminium atau racing baik standar pabrik atau produk aftermarket, umumnya jika sudah bengkok ternyata juga bisa diperbaiki dan tergantung dari tingkat kerusakannya. Bisa mengandalkan jasa perbaikan pres pelek untuk melakukan hal perlu diingat sebelum melakukan perbaikan, tentunya perlu mencari referensi bengkel pres pelek yang bagus agar mendapatkan hasil maksimal. Termasuk metode perbaikan apa yang dimiliki bengkel. Karena sebenarnya pengerjaan ini juga memiliki risiko tinggi jika tidak dikerjakan dengan dilakukan oleh mekanik bengkel yang bukan ahlinya, bisa saja dapat merusak bentuk dari pelek yang berujung pada pengeluaran biaya lebih besar hingga penggantian pelek sebelum melakukan perbaikan, konsultasikan dulu masalah dan tingkat kesulitan pengerjaannya. Karena pada dasarnya tidak semua kerusakan bisa diperbaiki oleh jasa pres pelek.
Prinsipdasar cara penanganan, pemeriksaan dan pemeliharaan dari peralatan angkat. 3. Kalkulasi yang ada. The reversible operations of making a connection Step by step hoisting operations 1. Cara yang harus dilakukan adalah mengatur tegangan brake band dengan mengatur ajusting hold down terhadap equalizing joke.
Merupakancara produksi yang paling efektif dalam pengaturan manusia, barang, equipment. Membuat standard supaya tidak digerakkan / tindakan sendiri tanpa instruksi atau persetujuan o Yang tidak mempunyai standard (tidak ada perbedaan normal / abnormal) pastilah tidak memiliki kaizen a. Tiga alasan standarisasi kerja a.1. Difokuskan pada kerja
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cara memperbaiki step motor yang bengkok
