Chapter 4 - Robot Drive Systems

Question 1

Direct Drive?

Answer 1

An electric drive in which no gear mechanism is used. The joint shaft is coupled to the rotor of the motor.
Requires very high torques

Question 2

Indirect Drive?

Answer 2

The joint is connected to the drive motor through a transmission mechanism. Doesn’t require very high torques. Lighter and smaller

Question 3

Work?

Answer 3

Whenever a force acts so as to produce motion in a body, work is done.

Work is done when energy is transferred to an object. When work is done energy is converted from one form to another.

The standard unit of work is the joule (J). One joule of work is accomplished when an object is moved 1 meter against an opposing force of 1 Newton.

1 joule = 1 Newton-meter

Question 4

Energy?

Answer 4

When work is done, energy is converted from one form to another. Therefore, energy can be defined as the ability to do work.

Question 5

Kinetic and Potential Energy

Answer 5

Kinetic Energy - is possessed by a body by virtue of its motion i.e moving car or a bullet

Potential Energy - is possessed by a system by virtue of its position or condition i.e compressed spring or a lifted object

Question 6

Power?

Answer 6

Power is an indication of how much work can be accomplished in a specific amount of time. Power can be defined at the rate at which work is done or energy is expended.

Because work is measured in joules and time in seconds, power is measured in joules per second. Standard unit for power is the Watt (W)

One watt (W) is the rate of doing work when one joule of work is done in one second.

Question 7

Torque?

Answer 7

A rotational force, which causes a change in rotational motion.

Question 8

Electromechanical Drives?

Answer 8

Consists of servomotors, stepper motors and pulse motors. They convert electrical energy into mechanical energy to power the robot.

Question 9

DC motors?

Answer 9

Any motor used in servomechanism.

They have a winding that is driven by the error realized when their is a difference in actual position and set point.

Types: Wound-field, permanent-magnet, and printed-circuit.

Question 10

Stepper motors?

Answer 10

Are controlled by a series of DC pulses. It changes electrical pulses into proportional mechanical movement.

Question 11

Chopper?

Answer 11

Used to control DC motors electronically. They convert fixed DC voltage to varying DC voltage.
Ex: Pulse Width Modulation

Question 12

Solenoid?

Answer 12

A current-carrying coil that provides magnetic action to perform a variety of work functions

Question 13

Servomechanism?

Answer 13

A control system that incorporates a feedback circuit for process operation

Question 14

Driver?

Answer 14

The gear closest to the source of the power

Question 15

Driven?

Answer 15

The gear being powered by the driver

Question 16

Linkages?

Answer 16

A linkage is a system of links connected at joints with rotary of linear bearings.

Mechanical linkages are intended to produce an output that is different from the input, by altering the velocity, acceleration or motion.

Question 17

Efficiency of a Drive System?

Answer 17

Overall efficiency of a drive system is measured as the ratio of the output power to the input power.

Belts, pulleys, electrical and fluid systems all lose energy due to friction, backlash, etc.