Placas de ampliación de troncales de CO

Definitions

) Kinematic chain - collection of links and joints

) Link - minimum non moving segment of a kinematic chain ) Joint - minimum moving part of chain. A joint consists of 2

links and an axis. There are 2 types of joints. Y Revolute joint - rotates around axis

Y Prismatic joint - linear movement along axis

L => link J => joint

NOTES:

Must be in Modeling mode to define kinematics.

Kinematics chain has an order established by the relationship of the links. The parent link precedes a child link in the sequence order. When the parent link moves the child link will follow. The parent takes the child with it.

In a kinematic chain, the number of links is equal to 1 more than the number of joints. For example: if there are 6 joints, there will be 7 links.

Methodology to Define a

Kinematic Device

Y What are the links, what type of joints, and so on) 2 Create the links

3 Verify that all entities have been selected as part of a link

4 Create the axis for each joint

Y An axis is defined by its two end points. The positive direction is from the first point to the second. (right hand rule)

5 Define each joint (parent link, child link, axis and joint type) Y Joints are defined between one object/assembly to a

second object/assembly. The father is the stationary object. Axis (right hand rule)

Child link

Parent link

6 Define the device.

7 Store component prototype

8 Test joints on mechanism using joint jog 9 Define a range for each joint 10 Define the device 11 Test joints in the device again

EXERCISE 1: Add Joints to a Simple

Component

Objective: To add joints to the door

The completed example is called room_door_demo that your instructor showed you. You will open the component called

room_door and add the joints to it.

1 Verify that you are in the projects/model_kinematics project. If you are not, then change your project.

Y Open a new workcell in the projects/model_kinematics folder.

2 Verify the menu you are on should be MENU: Modeling. This is printed above the top Menu bar. If it is not then, change it to modeling.

Y On the Top Menu window, select Robcad -> Modeling. 3 We must open the room_door to add the joints to it.

Y On the Top Menu window, select Files. Y On the Files window, select Open. Y For Component select room_door Y Click the Independent button. Y Click Accept.

4 Envision the kinematic chain. There are only two joints in this case. One for the door at the hinges and another for the handle.

Y First Joint: The doorframe is fixed and does not move when the door opens. So, this link will be the parent to the door hinge joint. The door will be the child link to the door hinge joint.

Y Second Joint: The next joint goes through the center of the door handle. Relative to the door handle joint, the door is the parent link and the handle is the child link.

NOTES:

The links and axis have already been created for you. All you have to do is define the joints and the mechanism.

5 Define the first joint:

Y On the Top Menu window, select Kinematics. Y On the Kinematics window, select Joint / Create. Y For Parent Link select door frame

Y For Child link select the door

Y For Axis select the line though the hinges Y For Joint Type click the Revolute button. Y Click Accept.

6 Define the second joint:

Y On the Kinematics window, select Joint / Create Y For Parent Link select the door

Y For Child Link select door handle

Y For Axis select the line though the handle Y For Joint Type click the Revolute button. Y Click Accept.

7 Define mechanism:

Y On the Kinematics window, select Robots / Define

NOTES:

A message should be printed below the Graphics Window that says Device has been defined

PRINCIPLE:

You must define the mechanism every time you modify the kinematics. Current joint values are saved for home position when define is selected.

NOTES:

Kinematics -> Query/Mechanism displays kinematic details of the mechanism in the Status Window.

8 Save mechanism

Y On the Top Menu window, select Files

Y On the Files window, select Save 9 Test the joint in mechanism

Y From the Toolbox Manager window, click Device Jog .

Y For Active mechanism pick CURRENT_MECHANISM

Y For Joint select J1

Y Move the mouse into the Graphics Window; hold down the

middle mouse button; move the mouse left and right to see the selected joint move.

Y For Joint select J2

Y Move the mouse into the Graphics Window; hold down the

middle mouse button; move the mouse left and right to see the selected joint move.

IMPORTANT:

Select Reset Mechanism on panel before saving the component or defining it again.

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HELP YOU FIND THE PROBLEM

1 Verify that all entities have been selected as part of one of the links:

Y On the Kinematics window, select Query / Link list

NOTE:

The list of defined links is displayed in the Status Window.

2 Blank by entity one link at a time

Y On the Top Menu window, select Display.

Y On the Display window, select Blank / Entity

Y For Type enter: k1

Y On the Display window, select Blank / Entity

Y For Type enter: k2

Y On the Display window, select Display / All

3 If there is an entity remaining, add it to the correct link.

Y On the Top Menu window, select Kinematics.

Methodology for Defining Device