Embedded Files
The goal of this phase of the project is to design a functional grasping mechanism that will successfully interface with the payload designed in Phase 1.
The goal of this phase of the project is to design a functional grasping mechanism that will successfully interface with the payload designed in Phase 1.
Design Constraints
Design Constraints
Within Phase 2 many constraints were involved with this portion of the project. Constraints are placed to set as a guideline to not only challenge, but to ensure direction and the ability to accommodate any given circumstance. The explicit constraints placed upon this phase of the project include:
Form
The weight of the design with all the links and parts summed up is approximately no more than 450g or approximately 1lb
Servo Motor
The Servo could not be touching any linkage that interacts directly with the payload.
The degree of the Servo was constrained between a 180 degree rotation. (90 degrees in each direction)
Materials
1/4" plywood was to be used to create each of the links used within the grasping mechanism.
Each part may be glued together using wood glue, if needed.
The grasping mechanism was to be actuated by a MG996R - 180 degree Servo Motor
Payload
The payload may be grasped and picked up at any point along the midline of the test rig.
The arm must have the ability to raise the payload 1.5" off the ground and return it to the correct placement without dropping it.
Throughout the entire process of the payload being grasped, picked up, and released, the payload must remain undisturbed.
Not only are explicit constraints entailed within phase 2, but there are implicit constraints the team has encountered as well, such as:
To configure the Grashof Linkage Synthesis properly a payload change had to be made. Due to the choice of design for the grasping mechanism of one link interacting with the payload being stationary and the other being movable, an implicit constraint within the grasping mechanism led the team to change the design of the payload. This was an unforeseen constraint that is personal to the Team's designs.
The grasping mechanism must be able to grasp, lift, lower, and release the payload, without any disturbance to it. The payload itself places several constraints upon the grasping mechanism. Therefor the grasping mechanism design is quite dependent upon the payload.
As far as a team imposed constraint the team has decided on laser engraving into the wood of our final designs. The laser engraving will take place towards the end of Phase 4. Laser engraving will be a unique challenge to furthermore enhance our knowledge and experience with laser engraving.
Figure 1: Test Rig
Phase Duration
Phase Duration
The phase duration expresses the entirety of phase 2 with respect to time. The team was given a total of three weeks to complete phase 2. Within that three week time period the grasping mechanism was to be created. The mechanism was to be designed properly to interface with the payload created in phase 1. A Grashof Linkage Synthesis was to be configured into the grasping mechanism along with a fourbar linkage. Given the goal of creating a grasping mechanism many of the constraints listed above were given to pinpoint class theory to be placed into real world practice.
Brainstorming Session
Brainstorming Session
Pros:
Pros:
Potentially easier to grab the stationary object
Can provide equal force on each side so is no slipping
Cons:
Cons:
Double arm motion in design reduces the degrees of freedom
Adds more weight to the design with extra links
Pros:
Pros:
Single arm motion reduces number of links in design as well as overall weight
Less room for error with only one arm in motion
Cons:
Cons:
May be harder to precisely grab and replace payload with a stationary link
Pros:
Pros:
Single arm motion reduces number of links in design and weight
Less room for error with one arm in motion
Cons:
Cons:
Link's position connecting two side arms may make moving arms range of motion shorter
Final Design
Final Design
Final design Degrees of Freedom Analysis
The final design was chosen to be a single-arm motion grasping mechanism as shown above. The design was chosen for several reason which includes the single arm motion reduces the number of links in the design along with its weight. There would be less room for error with the single arm in motion compared to having two arms motion.
Solidworks File
Solidworks File
Below are pictures of the solid works file for the claw, including pictures of it in the open and closed positions, pictures showing the dimensions of the parts, as well as a video of it in motion.
Below are pictures of the solid works file for the claw, including pictures of it in the open and closed positions, pictures showing the dimensions of the parts, as well as a video of it in motion.
Closed
Open
Dimensions
Dimensions
Dimensions of The Linkages
Dimensions of The Linkages
Dimensions of The Ground
Dimensions of The Ground
Video of the Claw in Action
Video of the Claw in Action
Video of Claw and Payload
Video of Claw and Payload
Linkage Diagram
Linkage Diagram
Below are two pictures of the linkage diagram, one showing the dimensions of the linkages.
Below are two pictures of the linkage diagram, one showing the dimensions of the linkages.
Design Considerations
Design Considerations
Two main ideas that the team kept in mind while designing this claw were efficiency and reliability. During this design process the team was presented with a task, to lift a payload, and the team attempted to design a claw that would allow us to firmly grasp not only the payload specified within Phase 1, but any payload, quickly, firmly and without fail. The team chose to leave out any extra challenges in order to focus all of our energy on designing a claw that would serve one sole purpose for the time being. This claw may not be the most flashy design for now, but one with a set base that will complete its tasks every single time to the same standard. This set base leaves room for improvement not only for team customization but also for excellence within the near future.
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