Tag Archives: encoders

Encoders for Autonomous Mobile Robots

Whether it is AMR or autonomous mobile robots, AGC or automated guided carts, AGV or automated guided vehicles, various types of robots or robotics are increasingly important to the industry. They use these robots to move parts and materials from one place to another in every environment. For instance, goods move from manufacturing to warehouse, and thence to grocery stores to face customers.

It is important that these automated machines work correctly because precision is a vital requirement. This requires reliable motion feedback to the controllers. This is where encoders come in. For instance, autonomous motion applications requiring motion feedback are useful in steering assembly, drive motors, lift controls, and more.

The industry uses several automated carts and vehicles. They use them for lifting products and materials onto and from shelves and floors in warehouses and other storage areas. To do that reliably and repeatedly, these machines require accurate and precise motion feedback. This ensures that materials and products reach where they need to go, without incurring damages.

The Encoder Product Company offers to draw wire solutions, and encoders with rack-and-pinion gears provide reliable motion feedback. This ensures all lifts stop at the right locations, thereby moving materials and products safely to their destinations. Their motion feedback options for lift control involve Model LCX, for high performance with absolute feedback option, and Model TR2, a rack-and-pinion gear as an all-in-one unit.

The Model LCX135 is one of a draw wire series, providing an excellent solution for the control of lifts. Internally, incremental and absolute encoders provide excellent lift control feedback using the CANopen communication protocol.

Automated carts and vehicles require drive motor feedback. As they move around facilities like warehouses, the controller in these vehicles needs reliable motion feedback to ensure the motors are in the proper transit areas/corridors designated for them. The motion feedback also ensures they stop and start accurately.

Motion feedback devices from the Encoder Product Company provide this reliable, repeatable motion feedback. Their Model 15T/H is a compact and high-performance encoder. It is available in the blind-hollow bore or thru-bore designs. The Model 260 is a more economical and compact encoder with a large thru-bore design. The next model 25T/H is a high-performance 2.5” encoder. While Models 25T and 260 are incremental encoders, absolute encoders are also available, and they use the same CANopen communication protocol.

To ensure the correct drive path ad steering angle, the steering assembly also needs to provide precision feedback. Absolute encoders provide the best way to ensure proper motion feedback for these steering assemblies. This is because with absolute encoders it is possible to ensure smart positioning while providing the exact location while in a 360-degree rotation.

The Encoder Product Company offers several absolute encoders. Among them is the Model A36HB, a compact absolute encoder with a 36 mm blind hollow bore. Another is the Model A58HB, an absolute encoder with a 58 mm blind hollow bore.

Where safety is considered paramount, the Encoder Product Company offers redundant encoders. These are simple solutions and economical also. Using redundant encoders allows the application to rely on different technologies, ensuring at least one encoder will continue to function even when the other has failed.

Where Do You Use Encoders?

All kinds of mechanical systems use a critical component commonly known as an encoder. Large industrial machines performing delicate work, high-precision prototyping, or repeatable tasks use encoders predominantly. Production of advanced electronics also requires the use of encoders. Encoders can be linear, angle, or rotary and the electronics sector uses them in some form or the other. Semiconductor fabrication, with its small components and work areas, requires encoders of the highest resolution and accuracy.

Production of electronics often uses vacuum environments with unique ventilation. These environments require special types of encoders, including linear and angle types made specifically to operate with the temperature and gaseous conditions prevalent with vacuum environments.

CNC machines must maintain their accuracy and position even when operating with heavy spindles and workpieces, high speeds, and multi-axis movements. All the components need to work together for accurate milling, drilling, and boring. Encoders play an important role in the synchronous working of CNC machines. For instance, custom linear encoders guide the travel of the axes of a milling machine.

At present, the automation industry is striding ahead rapidly and requires capable encoders. Strausak, a grinding machine company, makes robotic arms that manufacturing environments use universally. Unmanned mechanical systems must rely on accurate and consistent measurement and motion provided by encoders.

Automated transportation, such as high-speed trains in Sweden, depends on custom-made absolute encoders. These encoders operate a redundant system for automatically controlling the speed and braking of the train when necessary.

The medical industry requires precision and accuracy along with safety for testing and treating the human body while developing new procedures in the lab. CT and MRI scanning machinery use exposed linear and rotary encoders for precision imaging and maintaining patient safety. Precision angular and linear encoder technology help radiation therapy, leaving no room for error.

For instance, GammaPod, the most advanced breast cancer treatment in the world, depends on absolute rotary encoders for operating its stereotactic radiotherapy system. The medical industry depends on encoders predominantly because of the precision necessary for safely and accurately testing and treating the human body.

Robotics often uses articulating arms for picking and placing objects and equipment in manufacturing plants. They also use mobile, guided, and automated robots, which, in turn, require encoders for their proper functioning. For instance, encoders provide automated systems with the necessary and effective position and speed feedback for allowing them to function with minimum human intervention. Robotics often uses low-profile encoders that can fit inside small robotic arms.

All types of encoders are available for serving the general purpose of measuring motion and providing signaling feedback. However, their capabilities, configurations, and applications vary significantly and widely. In every facet of life, encoders play a significant role. This is especially applicable in the industrial and technological world, where safety, accuracy, and precision are important parameters to uphold.

Knowledge of the encoder transfer function is important for selecting the proper resolution for incremental optical encoders and for tuning the regulator depending on the speed and torque of the application. The implementation of a proper control loop impacts the stability and performance of the application.

Different Types of Feedback Encoders

All closed loop systems use feedback to control speed and or position. This plays an important role in keeping equipment operating accurately and smoothly. When using feedback for the best benefits in an application, it is important to understand how feedback works, because a variety of devices as well as models is available for the purpose. The most popular among them are tachometers, Hall sensors, encoders and resolvers.

Tachometers are rotating electromagnetic devices. Typically, these are connected to the shaft of a motor, rotating when the shaft rotates and generating a voltage as a signal. The faster a tachometer shaft rotates, the larger is the magnitude of the voltage output. Therefore, the output signal is directly proportional to the speed of the motor shaft. The polarity of the output voltage indicates the direction of rotation, clockwise or counter clockwise.

Usually, analog or DC tachometers provide direction and speed information. When fed to a meter, this information can be used in servo control for stabilization. DC tachometers are the simplest of feedback encoders.

Hall Sensors
Hall sensors are solid-state electronic devices and they can sense or detect magnetic fields. The output of the sensor changes or flips whenever a magnet comes close to a Hall sensor. Therefore, a Hall sensor provides a digital output as either a high or a low voltage.

Hall sensors are used for brushless motor applications, providing information about rotor position. This works as an electronic commutation, with the controller using the information to turn on or off specific power devices applying power to the stator windings.

Encoders are simple mechanical-to-electrical conversion devices and turn mechanical rotary motion into velocity or position information for systems controlling motion. Encoders can be rotary, digital, optical or incremental types.

In its most basic form, and encoder consists of a light source, a mask, a coded disk and a photo sensor along with related electronics. After passing through the mask and the coded disk, light from the source is detected by the sensor. As the encoder shaft rotates, light is alternately passed through or blocked, making an alternating light and dark pattern.

The associated electronics converts this into an electrical signal representing high or low corresponding to light passing through or being blocked. The resolution desired for the application governs the number of lines etched on the coded disk. By counting the number of pulses, the position of the shaft relative to its starting position is known.

There are two types of encoders, classified as incremental and absolute. Absolute encoders generate a specific address for each shaft position throughout the 360-degree rotation of the shaft.