09.1 Project Proposal
RMD Project Proposal
Proposal Deliverables
Introduction
Tong’s cats often don’t receive as much attention as she would like to give them because of her busy schedule. Cats require both mental and physical stimulation to stay healthy and happy, and a lack of interaction can lead to boredom. The goal of this project is to design a mechanism that allows Tong to play with and entertain her cats even when she’s occupied with other tasks. This system not only keeps the cats active and engaged, but also gives pet owners peace of mind knowing their pets are receiving attention throughout the day.
Problem Statement
The complexities involved in solving this problem include several motion and stability challenges. For motion and coordination profile, the robot’s arm and rover base will be moving simultaneously. The two parts will be sharing motion to keep the toy within reach of the cat while navigating obstacles and maintaining torque balance to prevent tipping. For force profile, the robot must also manage forces from the cat’s interactions, absorbing impacts without losing stability or control. At the same time, the base must move around obstacles while keeping the arm steady. Cats sometimes have irregular and fast movements, so the robot must handle irregular forces and impacts while maintaining coordinated motion. Additionally, as the arm moves, it shifts the system’s center of mass, requiring the robot to actively maintain balance throughout all motions to avoid tipping or instability.
These cannot be accomplished using simple joints because the motions this robot will need to undergo are more complex than the joints can handle. The forces from the cat and any other obstacles may be too much. Also the lack of range of motion will not be sufficient enough for a successful final product because of how these joints won’t allow the arm to go 360° or go up and down. Especially since the center of mass will be changing at times, simple joints can’t adjust to make the robot stable.
Mechanism
The proposed mechanism will consist of several sections: a robot arm and a robot car. The robot arm will consist of a series of coupler linkages (L7, L9) with a ground link (L1) that is connected to the car chassis. The main mechanism that could solve our problem is the slider crank mechanism. In our setup, the slider crank mechanism (L2, L3) connecting ground to slider L4 is used to control the launching/retrieving of the toy. L6 and L5 are attached at both sides of sliders L8 and L4 to further assist that action by pulling L8 towards or away from the car chassis depending on if we are launching or retrieving. This motion will reel in the toy through the string that tunnels through L9 and is attached to the toy. Ideally, as the toy is reeled in, the robot arm is able to slither it around to imitate the behavior of their natural prey, like a mouse or a bug. The base that the entire robot arm mechanism is attached to will be a spur gear (G2) that is driven on the side by the pinion (G1), which is directly connected to a brushed DC motor. There will also be two springs in total, each one connecting each slider to the bottom of the sliding track, to create that launching force.
The following Gruebler equation calculations are ignoring the fact that the entire arm rotates.
M=3(9-1)-2(9)-2=4 DOF
For the slider crank to work properly, L2 needs to be long enough to pull L8 back enough to fully retrieve the toy but also short enough to not interfere with the gear’s movements at the base. To be able to pull the toy back the most, we would need to fully rotate L2 around. Thus, looking at purely the 4-bar slider crank mechanism, the Grashof condition that would satisfy that constraint would be if S + L < P + Q, where at least one link could make a full rotation.
Proposed scope
As described in our problem statement, our goal is to create an interactive mechanism that will autonomously play with a cat. Our solution is to create a mechanism with multiple axes of rotation and translation in order to achieve the desired motion. In order to quantify the success of our project, we will perform multiple velocity and position analyses with which we will aim to move faster than the cat and have significant freedom of movement. To do this, we will use different techniques that we learned in class in order to optimize parameters such as transmission angle for different linkages and position making sure that we have full range of motion in three dimensions. An area that would help with the project that is not necessarily related to the contents of the course would be computer vision. To ensure that the mechanism is able to autonomously interact with the cat, a camera will be used to detect the location of the cat in order to decide what actions to take.
Our problem statement and proposed solution are quite general, so much of the steps that we will take to achieve our final solution will occur after our first iteration of prototyping and testing.
Preliminary Design
Once we have approved your project, the final proposal should include some initial design
ideas. You do not need in-depth analysis at this point, but document some basic design
elements (i.e., kinematic diagram drafts, Gruebler equation, Grashof, etc.). These designs
might change throughout the project before the final demo and report.