Flying vision target position corrections | ElmoMC

Elmo Motion Control Ltd. • 60 Amal St., P.O. Box 3078 ,Petach-Tikva 49516, Israel

Tel. +972-3-929-2300 • Fax. +972-3-929-2322 • [email protected] • www.elmomc.com

Elmo’s “Flying Vision”, the Ultimate Solution for

“On-the-Fly” Target Position Corrections

Abstract

Some advanced motion control applications require a change/update of the target position

“On-The-Fly”. Usually, the position change is a result of some position error detected by a

vision measurement system.

The goal is to set the process so that “fast movement towards the final target - capture of the

picture - calculating the correction - execution of the new position” is achieved while moving

and at max possible speed.

The whole throughput of the machine

depends on fast, smooth and stable position

corrections.

This could be the case in Pick & Place

machines where the alignment of the “picked”

component should be corrected according to

measurement done by the vision system, or a

wire bonding application where the final

target must be corrected according to vision

measurement.

Elmo’s “Flying Vision” is a unique and optimal solution for all type of “On-The-Fly” position

updates without reducing the process speed, and at maximum accuracy and stability. In some

cases Elmo’s “Flying Vision” improved the process speed by more than 30%.

The Flying Vision is an optimal Solution for any machinery whose process requires position

correction while moving at high speed and stable and smooth movements such as: PCB

Drilling, Flying probes, “Cut to length”, etc...

The Challenge

Each Machine drives two Gantries simultaneously, each Gantry system consist of five Elmo

Gold servo drives:

• X1,X2 – Operating As Master-Slave in MIMO based Gantry control architecture

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• Y – working as a 2 dimensional

Synchronized MCS (Machine

Coordinate System) grouped axis

with the X1,X2 Gantry axes

• Z – Vertical Axis

• Theta – Advanced miniature Elmo

servo drive for the Rotational axis

All ten drives in the system are operated using a single Elmo Multi axis controller (G-MAS)

via fast deterministic EtherCAT network.

A special fast vision system is located on each Gantry Path, where each SMT Pick & Place

motion trajectory cycle must pass through the constant position and location of the Camera.

This motion must proceed at the highest possible speed and precision. One of the key

elements of this solution is to pass through the camera location from different pick & place

position locations at high speed and smooth motion without stopping it during the Camera

snapshot photo.

When the SMT component arrives just above the

Camera location 2×OC (Tabulated position based

Output Compare) functions must be triggered as an

indication to the camera.

• 1st OC for powering up the Flash LED just

before the photo snapshot

• 2nd OC to Trigger the Camera for taking the

SMT rotational angle snap shot

The photo image information is processed by an upper level host computer or directly by the

camera, producing the final rotational and X,Y offset coordinates to the relevant axes in the

system just before the component final placement. The Host Computer is able to send the

final coordinates to the G-MAS during motion via the EtherNET network, as it has relatively

abundant time to process the data and send the final offset coordinates from the moment of

taking the photo snapshot until a few mili-seconds just before the final placement position.

Elmo Solution …

The Elmo solution for Distributed Gantry Control, eliminates excessive field bus network

loads, by implementing a propriety serial communication channel between the gantry servo

drives. One axis is logically defined as a Gantry Master, retrieving all the required

information from the slave, computing all MIMO control laws, while keeping the system fully

synchronized to the drive PWM level. This kind of structure eliminates the G-MAS from

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handling the Gantry MIMO control algorithm operation and therefore regards the X1, X2

gantry drives as a single X axis drive on the network level. This “single axis” is grouped with

an additional Y axis in order to perform the fast synchronized X, Y 2-dimensional motions of

the machine.

Elmo suggests two possible mechanisms for the solution of this machine. As previously

mentioned, the key element of this solution is to perform highly X,Y synchronized motions

while passing through the camera position location at high speed, and precision, using high

speeds with a smooth motion profile in both Position, velocity and Acceleration/Deceleration.

The first solution is to use a 2-dimensional

Spline motion. Elmo support several

operation modes of Spline trajectories

building. One of the methods, that most

suitable for this solution allows the user to

define a predefined table of spline

positions limited by a vector velocity,

Acceleration/Deceleration rates and Jerk.

Using 2-Dimention X,Y tabulated splines

ensure to pass through all spline defined

positions at the highest possible speed and

maximum precision.

The Second solution involves special

polynomial function block mechanism.

This advanced G-MAS functionality

allows one to build a complete

synchronized motion trajectory using

special segmented motion function blocks.

In this mode, the user defines an auxiliary

and final position points as part or as the

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whole motion trajectory. The G-MAS profiler will pass through the auxiliary predefined

position using a polynomial transition trajectory. This advanced capability allows the user to

build in a relatively simple way complex motion trajectories that allow position, velocity,

smoothness in acceleration/ deceleration and limited jerk.

Using the “speed override” function, the G-MAS can accelerate / decelerate the speed of the

motion trajectory as a function of the waiting time, until it receives the final X, Y and

rotational coordinates from the camera during its motion. This function optimizes the speed to

maximum, achieving an optimized timing for the motion on each Pick & place cycle.

An additional powerful G-MAS feature is that this solution can employ superimposed

motions. The G-MAS allows “linking” a virtual axis to any stand alone or grouped axis of the

system. The superimposed sum positions of the real and virtual axis trajectories are the final

position of the real axis trajectory. This capability allows adding an offset position to any axis

in the system “on the fly” during motion while performing the original motion trajectory that

is predefined by the motion function block, without changing overall motion time.

Two tabulated OC functions are used for operating the flash and triggering the camera as a

function of the motion trajectory position. This functionality allows high synchronization

between the Camera operation and the motion generated by the G-MAS.

Why Elmo:

• Suggest advanced full motion control solution for this type of machine

• Applying advanced Gantry MIMO control solution

• Regard the Gantry Master-Slave axes as simple one axis on the network

• Using splines and polynomial function blocks to create optimized motion trajectories

• Full “on the fly” trajectory control during motion time

o Control the motion process timing using Speed Override functionality

o Control the motion process final position offset using positioning Superimposed

functionality

• Extremely fast and precise trajectories motion control

• Simply test your complex motion profiles using build in EAS (Elmo Application

Studio Software) tools

• Digital Signal Output triggering to the camera using one of the OC function available

methods

• High power, advanced miniature size servo drive for the rotational axis

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Technology

Flying vision target position corrections | ElmoMC