Robot Power and Drive Systems 265

"Robot Power and Drive Systems 265" is an overview of the systems and mechanisms that provide power and motion to an industrial robot. Robotic drive systems use a drive to control and feed electricity to a motor, or actuator, that converts power into motion within the robot's joints and components. The main types of actuators are hydraulic, pneumatic, and electric motors, with electric motors being the most common.

Together, drives and actuators form a drive system. Drive systems, along with transmission systems, control various degrees of speed and torque to generate motion in a robot and its components. This control affects the precision, accuracy, and efficiency of industrial robots. After taking this class, users will be able to identify and describe common robotic drive system components and their basic functions.

Class Details

Class Name:
Robot Power and Drive Systems 265
Difficulty:
Intermediate
Number of Lessons:
12

Class Outline

  • Power in Robotics
  • Hydraulic Drives
  • Pneumatic Drives
  • Electric Drives
  • Drives Review
  • Servomotors
  • Stepper Motors
  • Gear Systems
  • Transmission Systems
  • Motion and Position Sensors
  • Motion Control Systems
  • Final Review

Objectives

  • Describe power for industrial robots.
  • Describe hydraulic drives.
  • Describe pneumatic drives.
  • Describe electric drives.
  • Describe servomotors.
  • Describe stepper motors.
  • Describe robotic gear systems.
  • Describe robotic transmission systems.
  • Describe sensors and their use within drive systems.
  • Describe motion control for robot drive systems.

Job Roles

Certifications

Glossary

Vocabulary Term Definition
AC Alternating current. Current that reverses direction at regularly recurring intervals of time. AC is usually converted to DC by robot power systems.
accumulators A fluid system component that stores pressurized fluid from the pump as an auxiliary source of fluid power. Accumulators can be controlled to release hydraulic fluid as necessary at the required system pressure.
actuator A device that converts energy into linear or rotary motion. Actuators in robots can include electric, pneumatic, and hydraulic motors.
air compressors The power source of a pneumatic system that pressurizes ambient air. An air compressor directs pressurized air into the system in order to produce mechanical power.
alternating current AC. Current that reverses direction at regularly recurring intervals of time. Alternating current is usually converted to DC by robot power systems.
amplifier A device that increases the size or strength of a signal. Servomotors use amplifiers as part of the motor control system.
armature The part of a motor in which a current is induced by a magnetic field. The armature usually consists of a series of coils or groups of insulated conductors.
ballscrews A threaded device that rotates to provide precise linear motion. Ballscrews are often powered by servomotors.
bearings A friction-reducing device that allows one moving part to glide past another moving part. Bearings operate using sliding or rolling mechanisms.
belts A band of flexible material that is looped around two or more fixed pulleys to transmit motion. Belts are made of various materials and come in different types, such as flat belts, round belts, and V-belts.
bladders An expandable, flexible bag that can be filled with air or liquid. The bladder in an inflatable gripper expands inside of a container for handling.
brushless DC motors A DC motor that uses a permanent magnet instead of brushes to run the motor. Brushless DC motors are the most commonly used actuator.
brush-type DC motors A DC motor that has internal commutators. In brush-type DC motors, internal, rotating brushes create the electrical connection.
cartesian robot A type of robot that moves along three orthogonal axes. Cartesian robots have linear joint movement that gives them a highly rigid structure, allowing them to lift heavy objects.
chains A device made of individual links that mesh with the teeth of a sprocket. Chains are used in chain drive systems to transmit motion.
closed loop Part of a system that uses feedback from a sensing device. Closed loop servomotors are a common robot actuator.
commutation The process of creating or reversing an electrical current. Commutation can be performed manually of electronically.
commutator A device connected to the rotor of an electric motor that makes an electrical connection and ensures that the current flows as direct current. Commutators include the brushes of a brush-type DC motor.
conductors A fluid system component such as a pipe, tube, or hose. A conductor conveys liquids or gases throughout a fluid system.
conductors A material or element that allows free movement of electrons and therefore allows easy flow of electricity. Conductors are typically metals.
control valve A mechanical device that regulates the flow of fluid or gas by opening, closing, or obstructing one or more passageways. Control valves control the pressurized fluid that creates motion in hydraulic drive systems.
controller The main device that processes information and carries out instructions to a robot. A controller operates an entire robot system.
DC Direct current. Electricity that flows in one direction. DC runs most robots.
direct current DC. Electricity that flows in one direction. DC runs most robots.
direct drives A drive train system that uses a straight shaft to connect the motor immediately to the output device. Direct drives require precise, rigid alignment.
double helical gears A type of helical gear with two sets of teeth cut at opposing angles and separated by a groove that runs around the center of the gear. Double helical gears are used to provide smoother operation.
drive An electronic device that takes the command signals from the controller and then controls the acceleration and deceleration, speed, and power of an electric motor. In robots, drives are connected to electric motors.
drive pulley The fixed pulley in a belt drive system that receives energy from the power source. The driver pulley transfers energy to the driven pulley via the belt.
drive system A group of devices that provides the mechanical power and motion for robot components. Drive systems include a drive and an actuator, such as an electric motor.
driven pulley A fixed pulley in a belt drive system. The driven pulley receives energy from the drive pulley via a belt.
electric actuators A device that creates power by an electrical circuit. Electric actuators are the most common drive used in robots.
electromagnet A powerful magnet that gains an attractive force only when current passes through it. Electromagnets can be turned on and off with a switch.
encoder A device that translates rotary or linear motion into a digital signal. Encoders are often mounted to the servomotor of a robot.
end effectors A device attached to the end of a robot arm in order to interact with a part, component, or material. The end effector, or end of arm tool, may be a gripper that allows the robot to pick up objects and place them down.
feedback A return signal that confirms a condition of a robot, such as position. Feedback devices include proximity sensors and encoders.
feedback Information sent from a sensing system to show performance information, including abnormalities and errors. Feedback allows the system to adjust the robot's position or force.
fixed pulleys A circular device that is used in belt drive systems to transmit motion. Fixed pulleys rotate around an axis that does not move.
flow control valve A fluid system component that controls the rate of air flow. Flow control valves make it possible to control the speed of the actuator.
flow rate A pneumatic power variable that describes how much air is being moved and how much work is being performed. Flow rate is usually measured in cubic feet per minute or cubic meters per minute.
gear ratio The relationship between the number of teeth on two meshing gears, or the number of times one gear turns in relation to another gear. The gear ratio reflects the change in mechanical speed and torque from the motor.
gear shafts A cylindrical bar used to support and rotate gears. Gear shafts connect gears to other components, such as actuators, to transmit rotary motion through a mechanical system.
gear train A system of gears used to transmit rotary motion from one part of a mechanical system to another. Gear trains contain two or more meshing gears.
gears A wheel-shaped device with teeth around the perimeter that is used to transfer force and motion to another device. Multiple gears often interconnect with one another to transfer motion.
grippers A dexterous material-handling component that resembles and performs similarly to a human hand. Grippers allow robots to perform tasks such as handling small parts and can be powered by pneumatic systems.
Hall-effect devices HED. A device that detects voltage differences in order to switch circuits off and on. Hall-effect devices are often used in brushless DC motors.
helical gears A type of gear with slanted teeth. Helical gears are quieter than spur gears, but they are more expensive.
hydraulic actuators A device that creates power by the controlled motion of a liquid. Hydraulic actuators are often used with robots that must lift heavy loads.
hydraulic pump A mechanical power source that creates fluid flow and moves fluid through a hydraulic system. Hydraulic pumps receive energy from a prime mover, such as a motor or engine.
industrial robots A reprogrammable machine sometimes used in place of a person in a manufacturing setting. Industrial robots perform dangerous or repetitive tasks with a high degree of accuracy.
joints A connecting component on a robot that can move through an angle about a center point. Joints on a robot mimic the movement of human joints, such as a wrist or elbow, with the ability to rotate.
Laser interferometers A device that projects a laser onto reflectors mounted to objects and other surfaces to gather spatial information. Laser interferometers can give precise position feedback.
linear variable differential transformers LVDT. An electrical device that measures linear displacement. Linear variable differential transformers can provide motion and position feedback in robotic systems.
links A rigid body between two joints. Links are moved by actuators within the joints.
machine learning ML. The process that enables a digital system to analyze data in order to build predictive models. Machine learning systematically solves problems using highly complex algorithms.
mechanical energy Energy transmitted through the physical interaction and motion of instruments or tools. Mechanical energy is used to perform work.
motion control Controlling the movement of machine elements. Motion control is produced by using a mechanical source of power like an actuator.
motor A machine that converts one form of energy, such as electricity, into another. Typically, an electric robot motor converts electrical energy into rotary motion.
on/off devices A mechanism with a simple control that allows it to be turned fully on or fully off. On/off devices are either in operation or not, without any intermediate states.
open loop A type of control system that uses an input signal without gathering output or feedback. Open loop systems include stepper motors in robot applications.
path planning Robot software that uses algorithms to direct the robot's motions through space. Path planning software finds the safest and most efficient route for a robot to complete a task.
permanent magnets A magnet that retains its attractive force after it is removed from a magnetic field. Permanent magnets have high residual magnetism.
pneumatic actuators A device that creates power by the controlled motion of gas, usually air, under pressure. Pneumatic actuators are often used to power robotic grippers, simple pick-and-place devices, and robots where electric motors might pose a hazard.
point-to-point motion Movement with end positions but without specified paths to reach the end positions. Point-to-point motion does not require precise movement between points and is an appropriate application for pneumatic drive systems.
pressure relief valve An adjustable control valve that regulates pressure in a hydraulic system. The pressure relief valve releases when the hydraulic system exceeds the necessary amount of pressure.
reservoir The main storage container for fluid in a hydraulic system. The reservoir supplies fluid to the hydraulic pump.
resolvers An electrical transformer that measures rotation for position and velocity feedback. Resolvers are analog devices used in some servomotor applications.
robot control system A network of control loops used to manage dynamic processes in robots by adjusting or maintaining physical variables. Robot control systems create more precise and repeatable processes.
roller chains The most common type of chain used in industry. A roller chain can be used at high speeds.
rotor The rotating part of a motor. The rotor connects to an output shaft that drives the load.
sensor A device that detects a change in a physical stimulus and turns it into a signal that can be measured or recorded. Sensors allow robots and other devices to interact with their environment and monitor operations.
servo drives A motor control device that outputs electrical signals to a servomotor to induce motion. The servo drive can be built in as part of the motor or it can be a separate device.
servomotor A small motor used in robots to allow for precise movement. Servomotors are often used in several places in a robotic arm, including the elbow joint and the gripper.
shaft The rotating part of a motor that s connected to the rotor and transmits torque to the load. The shaft turns and transmits that motion to the robot component.
speed The rate at which a whole robot or part of a robot travels. Faster speeds enable quicker robot motion but can often lead to less precision of movement.
sprockets A gear or wheel with metal teeth that mesh with the links of a chain. Sprockets are used in chain drive systems to transmit motion.
spur gears A type of gear that has straight, flat-topped teeth set parallel to the shaft. Spur gears are the most common type of gears used in industry but are not ideal for high-speed applications.
standard inverter drives A device used in drive systems that helps control motion by sending different frequencies and voltage of electricity. Standard inverter drives are common in electric motor drive systems.
stator The stationary part of a motor. The stator houses the motor's rotor and windings.
stepper motor A type of electrical device that creates mechanical movement in small, precise increments. Stepper motors are often used in open loop systems.
synchronous belts A toothed belt that meshes with the grooves of a pulley in a synchronous belt drive allowing it to maintain constant speed during power transmission and avoid slippage. Synchronous belts permit higher speed and greater precision.
tachometers A device measuring the rotation speed of a shaft, as in a motor. Tachometers are good for gathering velocity feedback in robotic systems.
thrust load A force that attempts to shift a component off its axis of rotation. Thrust loads occur when gear teeth mesh together at an angle.
torque A force that produces rotation. Torque can be increased or decreased by a transmission system.
transmission A machine that uses a combination of gears and other mechanical components to change the speed or torque of mechanical energy. Some transmissions can also change the direction of mechanical energy.
vacuum grippers A device that uses flexible suction cups and vacuum-controlled airflow to attach to parts. Vacuum grippers allow robots to perform tasks such as handling and moving parts.
valves The internal component that covers a port. The valves open and close to allow or block flow.
velocity The rate of change in an object's speed in a given direction. A constant surface speed ensures a steady velocity.
windings Wire that is wrapped around a core or into a coil and used to conduct current. Windings connect to pole pieces to form electromagnets and magnetic fields in motors.
worm gears A gear with teeth that mesh with the screw-like threads of a shaft, called a worm, to transmit motion. Worm gears are usually the driven gears in worm gear sets.