Jog, Home to Marker, How Motion Works

5 How Motion

Works

5.1 Introduction

The SM-EZMotion module offers four different motion object types. These four types are Jog, Home, Index, and Gear. All motion objects run on what is called a Profile. Only one motion object can run on a Profile at a time. For applications that need to run multiple motion objects simultaneously, the SM-EZMotion module has two different Profiles. This will be discussed further in the Summing Multiple Profiles subsection below.

This section will concentrate on how the different motion objects work, and not on how they are configured using PowerTools Pro. For more information on how to configure the motion objects in PowerTools Pro, see “Configuring an Application” on page 33.

5.2 Jog

Jog is a motion object that has Acceleration, Velocity, and Deceleration, but no dedicated distance. The user pressing a push button or foot pedal often controls jog motion. When the user presses the Jog button, the jog accelerates up to the jog velocity and continues to run at that velocity until the user releases the Jog button. When the user releases the Jog button, the jog decelerates from the Jog Velocity back down to zero velocity (stopped).

Figure 32shows an example of a Jog profile.

Velocity
	Jog Velocity
Jog Accel	Jog Decel
	Time

decelerate to a stop immediately (called Calculated Offset), or continues at the Home velocity and comes to a stop a specified distance from where the reference signal activated (called Specified Offset).

The Home is typically used to define a reference position (or Home position) on a machine. This can be done in several different ways depending on what type of Home Reference is used. The Home Reference determines what action or signal defines the Home position. The three types of Home Reference supported by the SM-EZMotion module are Marker, Sensor, and Sensor then Marker. Following is a description of the three different Home types.

5.3.1 Home to Marker

Most motors used with the Unidrive SP have an encoder mounted in the back end of the motor. This encoder is used to feed positional data back to the Unidrive SP or SM-EZMotion module for position control. Each encoder has a special signal called the Encoder Marker Channel that activates once every revolution of the motor. The SM-EZMotion module can use this Marker as a reference signal when executing a Home.

The Marker provides an extremely accurate means of homing the system. The SM-EZMotion module will detect a rising edge of the Encoder Marker signal every revolution of the motor shaft. The Home routine begins by accelerating up to the Home Velocity. The motor continues at the Home Velocity until the Encoder Marker activates. The motor then decelerates to a stop immediately, or continues for a specified offset distance. Figures 33 and 34 show examples of the Home to Marker profile, with calculated offset and with specified offset respectively.

Velocity

Home Velocity

Home Accel

Home Decel

Time

Jog.PlusActivate

Figure 32: Jog Profile Diagram

The distance traveled by a Jog is entirely dependant on the duration that the Jog signal is held active. To accurately control the distance the motor moves, an Index is the preferred motion object type.

5.3 Home

Home is a motion object that has Acceleration, Velocity, and Deceleration. A Home works by accelerating up to the specified velocity until a reference signal activates. Once the reference signal activates, the motor either begins to

Home Initiate

Encoder Marker

Emerson P/N 400361-00 manual Jog, Home to Marker, How Motion Works

Models: P/N 400361-00