Three separate areas are under consideration for a kinematic coupling:
Each area has five possible coupling options:
This page lists the current benefits (+), problems (-), things
to be investigated (?), and current status of each option. The current and
future proposals or work are listed for each area of the robot. The
current proposal represents the current suggested design, which has been
requested by ABB for late October. The future proposal/work details the
direction that the graduate students feels the research is heading and presents
a concept for the final design. This concept may change frequently.
In addition, downloads such as design tools and presentations are separated for
each coupling area. This page will be kept updated with current
information for each type of coupling option and coupling area.
Updated 08/20/2002 06:31 PM
|Standard||Proposed Design using grooved insert plate on flange||- Changes flange geometry
- Requires alignment features in flange
+ Most compact solution
|Three Pin Coupling||Design is still a possibility. This coupling would be used only for static measurements and would be removed from the robot afterwards. Current spreadsheet can be found under design tools below with a power point presentation describing the features.||- Requires a separate interface plate
- Complicated arrangement of bolts to use with tool
- Cannot be used while robot is moving quickly
+ No changes to flange
? Investigate if coupling provide adequate precision and repeatability
|"Ping Pong Paddle" Interface Plate with Arm||Design is no longer under consideration since pin cannot supply a sufficient force to secure the coupling. In addition, the small pins would most likely not be able to withstand the high emergency torque values.||- More complicated design
- Requires knowledge of forces and moments present at flange interface
-Arm will be in the way for some operations or catch wires/tubes and twist them
- Arm will interfere with robot wrist
-/+ Requires tooling to bolt onto flange through the interface plate, but simplifies use of Wonder Wyler unit
+ Can use Wonder Wyler without removing tool
|Quasi-Kinematic||Not Considered||Not required for design|
|Canoe Ball||Not Considered||Not required for design|
|Kinematic Wavy Spring Washer||Not Considered||Not required for design|
The current proposal uses the standard three ball and groove coupling. The grooves are machined into a plate which can be inserted into the center recess on the flange. In addition to the grooves, a recess is machined into the plates to hold the magnet. The insert plate will be attached to the flange using a method determined by ABB. For existing flanges, the most likely connection is to press fit the insert into the recess using an alignment method such as matching pins and holes between the parts or tabs on the insert that mesh with the existing bolt holes on the flange. For new tool flanges, it would be ideal for the grooves and magnet recess to be integrated into the flange so a separate insert is not required.
The balls for the coupling will be placed on two surfaces of the Wonder Wyler cube. For the prototypes, the balls were tooling balls purchased from McMaster-Carr Supply Company. The final product could use these parts, although it might be less expensive to machine them or consider a separate company. Both the balls and grooves should be of similar hardness material. These balls would be press fit into the side and bottom of the Wonder Wyler unit. At the center of the ball's triangle, a hole is threaded for easy installation and removal of the magnet.
The last section of the proposal is how to place individual grooves at other locations to be measured. Several variations of posts and holes can be used. The prototype has one thick post attached to the groove that is press fit into a corresponding hole on the robot. A thinner pin is pressed or threaded into the robot and will mate with a hole on the groove using a slip fit. The post fixes the location of the groove while the thin pin prevents rotation. This setup could be easily used in the final design. Another possibility is to have two posts on the robot and two holes on the groove. By correctly adjusting the height of the grooves, the magnet will rest on the robot or slightly above. This setup is particularly useful for the dynamic axis 1 measurement. For this measurement, the three grooves will be separated so that two grooves will be fixed on the outer edge of the base. The third groove is fixed on the inner area of the base which will rotate. The Wonder Wyler unit will fit onto the coupling and slide in the grooves as the robot rotates.
|Standard||Not Considered||- Requires modification to interface surfaces, specifically the
addition of hole for balls and grooves to be pressed into
- Cannot be packaged as an independent adapter kit (requires changes)
- Requires modification of arm length in computer due to space for coupling
|Quasi-Kinematic||Not Considered||Same as Standard|
|Canoe Ball||Prototypes Built, Tested in July 2001||Same as Standard
+? Probably the most precise and repeatable method available, need to investigate with respect to the kinematic washer
|Kinematic Wavy Spring Washer||Not Considered||- For direct application, requires modification of interface surfaces
but an adapter kit could be used
- Requires modification of arm length in computer to account for adapter plates
+ Adapter kit would consist of plates that fit each side of the interface and kinematic bumps on opposite side. Kinematic wavy spring washer will fit in between two plates.
? Investigate precision of plate to interface connection
|Three Pin Coupling||Prototypes Built, Tested in July 2001||- Requires removal of two of four control surfaces (four tabs on a
circle) and replacement of hollow pin with a smaller solid pin
+ No change in arm parameters
? Investigate if how precise it is compared to other options
Use three pin coupling with two control surfaces as the blue pins (see power
point presentation mentioned earlier) and a solid control pin (red anvil pin).
Bolt would pass through upper arm and apply pre-load to couple in the interface
plane. Current bolt system would still be used to secure the arm to the wrist.
January 11, 2001 Executive Summary for ABB