Motion Control

The Basics of Encoder Selection

Positioning: Resolution and Accuracy

An application’s required positioning resolution dictates the choice of encoder resolution. A well-tuned system can maintain the position within one encoder state (quadcount). Therefore, the encoder resolution in quadcounts (states) should at least correspond to the maximum permissible positioning error. Depending on the response time of the system, a higher encoder resolution should be chosen for the controller to detect deviations faster and counteract quicker.

Posted in: Articles, Motion Control, Calibration, Navigation and guidance systems, Navigation and guidance systems, Reliability, Reliability
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Choosing Stepper- or Servo-Driven Actuators to Replace Air Cylinders

Pneumatic (air) cylinders are widely used in industrial automation due to their low per-axis cost and high-speed/force capabilities. They have a long history of being popular workhorses in the automation industry. However, there are many reasons to use electric actuators in place of air cylinders: reduced machine downtime, reduced energy consumption, increased precision, and increased speed. In addition, electric actuators can be powered by servo or stepper motors, in conjunction with a control device, to provide linear motion.

Advantages of Electric Linear Actuators

Reduced downtime. Electric linear actuators (whether screw- or belt-driven) are very low-maintenance. Regreasing may be the only regular maintenance necessary, and many screw-driven models are lubricated for the life of the actuator.

Posted in: Articles, Aerospace, Motion Control, Sensors and actuators, Sensors and actuators, Electric motors, Durability, Durability
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Precision Robotics and Automation: Hexapods Advance Production Processes

Hexapods — six-legged parallel-kinematic machines — are quickly gaining ground in a broad range of industrial automation applications after “learning” how to directly communicate with PLC or CNC controllers via Fieldbus interfaces. As far as the semiconductor and electronics industry, automobile industry, and precision assembly are concerned, many production processes have become inconceivable without them. Today, the six-axis positioning systems are available with load capacity from 2 kg to 2000 kg, and travel from 10 to hundreds of millimeters while maintaining submicron precision. Hexapods are used for aligning the smallest optical components in the latest silicon photonics production processes, for controlling automated labeling machines, and positioning entire body parts for automotive production. The intrinsic hexapod features contribute to a wealth of new possibilities in robotics.

Posted in: Articles, Motion Control, Automation, Robotics, Optics, Optics, Kinematics, Automation, Production, Robotics
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Advantages of Servo Motor and Direct Drive Technology

For many years, stepper motors have been the most popular type of electric motor designed into instrumentation for a wide variety of reasons. Stepper motors have become increasingly commoditized, and can be sourced easily. In addition, the growing “maker movement” has simultaneously made them more popular and reduced their cost. Unlike servo motors, stepper motors don’t require tuning to optimize their performance. What’s more, scaling and motion commands are typically quick and simple to execute using stepper motors. Servo motors often require a bit more expertise in executing complicated (torque, velocity, or position) loop closures. Finally, micro-stepping allows most modern drive electronics to step or increment a stepper motor to a resolution of 50,800 steps per revolution or higher.

Posted in: Articles, Motion Control, Motors & Drives, Optimization, Energy conservation, Electric drives, Electric motors
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An Inside Look at Electromechanical Power-Off Braking Options

Making the right choice between spring set and permanent magnet brakes can impact safety, durability, maintenance, and performance.

Power-off brakes are designed to hold or stop motion in the absence of power. Adding an electrical current releases the brake, freeing the load for motion. Given the safety ramifications of keeping a system locked in place until it is powered up, motion control system designers tend to specify power-off brakes more often than power-on brakes. There are, however, two different failsafe brake technologies: one uses compression springs to hold its load in place, and the other uses permanent magnets. Each has specific strengths and weaknesses, and knowing the difference can impact safety, durability, cost, and performance.

Posted in: Articles, Motion Control, Electronic brake controls, Springs, Magnetic materials
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Simplified Machine Design Approach for Optimal Servomotor Control

An often asked question from industrial machine builders or integrators is how they can effectively design or implement the conversion of a machine with servo technology to meet performance expectations. This is a specialized task filled with layers of complexity that can prove difficult to execute, even when the scope of work is fully understood.

Posted in: Articles, Motion Control, Design processes, Sensors and actuators, Sensors and actuators, Industrial vehicles and equipment
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Robots and Humans - Let the Collaboration Begin

A collaborative robot is essentially an industrial robot with additional safety capabilities. These safety features include:

Safety-rated monitored stop (zero speed limiting) Speed and separation monitoring (limiting) Hand-guiding Power and force limiting (PFL)
Posted in: Articles, Motion Control, Human machine interface (HMI), Robotics
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Optimizing Drive Systems for Energy Savings

Energy savings are an extremely important topic in virtually every segment of industry today. In general, the largest consumer of power in a converting line or machine is the drive system. As energy costs continue to increase and energy conservation becomes a greater priority, are there technologies or methods that can be implemented to reduce the energy consumption on converting machinery?

Posted in: Articles, Motion Control, Energy consumption, Vehicle drive systems
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Choosing the Right Potentiometer for Reliable Sensing

In today’s market, there are a variety of available types of position sensing systems. It is important to compare unique features to application needs in order to find the best fit.

A potentiometer sensor is an electromechanical component that consists of a resistor where the voltage divider value can be measured at any position by means of sliding contacts between the applied voltage values. Physically, a potentiometer consists, at a minimum, of a resistance track, a collector track, and a sliding contact that can be moved along the resistance track by means of mechanics (Figure 1). The movement of the sliding contact can be rotatory (angle) or translational (path).

Posted in: Articles, Motion Control, Sensors and actuators, Sensors and actuators, Test equipment and instrumentation
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Imitative Robotic Control: The Puppet Master

Automated systems can have a hard time completing complex tasks in a timely manner. When controlling a robot outside autonomous mode, a good control device needs to give the user full control of the system while enabling the mission to be completed in a quick, accurate, and efficient manner.

Posted in: Articles, Motion Control, Robotics
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