8.1 - Initial Proposal

Introduction

When you’re busy working at your desk or driving a car, it can be easy to forget to stay hydrated and dangerous to take your hands off of the wheel, particularly in Texas. Since most tasks are designed to do with two hands, a third helping hand can be needed for the simpler things you need to do relatively frequently, like drinking water. This is a simple, repetitive task that people have to do often. We want to investigate a way to help people stay productive and safe while still meeting their basic hydration needs, and we intend to do so by implementing a simple system with complex motion.

Problem Statement

The process of drinking water from a bottle has multiple steps involved, each with different motion requirements and force profiles.

The first step is locating the water bottle.
The second is grasping the water bottle with enough force that the static friction is able to secure the water bottle against slippage from external forces.
The third step is to move the water bottle to the mouth. This motion occurs in all 3 planes: x, y, and z. You have to lift the water bottle to the appropriate mouth height, and rotate or translate it along the plane that the mouth is in until it is close to the mouth.
The fourth step is to rotate the water bottle towards the mouth so that water is able to pour out into the mouth.
The fifth step is to rotate the water bottle back until it is vertical again.
The sixth step is the reverse of the third step: move the water bottle back to its starting position via the motions detailed in step three.
The seventh step is to release the water bottle.
Lastly, the eighth step is to move the hand away from the water bottle.

Our mechanism will address steps three through six. The device will hold the water bottle when not in use, to avoid needing to locate and grab it each time. It will automate the process of lifting and rotating the water bottle for the user to drink from and returning it to its starting location. This process entails a complex but repetitive pattern of translation across 3 planes as well as rotation about an axis. These motions could be done in steps or in tandem, and the location of the mouth relative to the starting position could be variable or held constant. Although the motion itself is consistent, the forces required to enact each step will vary based on the weight of the water bottle. For even one iteration of the process, the water bottle will contain more water when bringing the bottle up to the mouth than when bringing it back to the resting position. This requires an application of different forces at each step, and variation of these forces between subsequent iterations.

Mechanism

The mechanism we have in mind to address this problem moves across all three dimensions, maintaining an upright cup, and using only one motor input. It does this by using a gear on a stationary “carousel” to move the cup towards the user in the x and y direction (see Preliminary Design Ideas). An arm attached to the gear lifts as the gear rotates to bring the cup up in the z direction.

In order to maintain a stationary carousel and spin the gear, the motor will need to sit on a rotating platform in the center of the carousel which is attached to the gear. A gearbox may be required to generate enough torque to lift the arm carrying the cup.

To keep the cup upright during the rotation, we will avail the force of gravity by setting the cup in a freely rotating holder, so that its own weight keeps it upright. This is similar to no spill bowls.

We may also make use of an encoder to keep the movement consistent with varying weight of cup, battery power, etc.

Proposed Scope

We will not address the problem of locating the water bottle in the first step as well as moving the mechanism away from the water bottle after each iteration of motion. The step of grasping and releasing the water bottle will be addressed if time permits, though the variable weight may increase the challenge of this step. We will attempt to design a mechanism that is able to complete the rest of the steps involved in the process of drinking water: moving the water bottle to the mouth, pouring water out of the bottle, and moving the water bottle back.

We will need to analyze the motion profile required for each subsection of the mechanism (hand, arm, anchor). This will help us design a linkage system that meets the necessary DOF and motion constraints for the process. We will also need to complete a force analysis that considers the external forces on the mechanism in each step and the forces that must be exerted by the mechanism on the external environment to complete each step. This will vary greatly dependent on the water bottle weight. We will cleave together the force and motion analysis to consider the velocity requirements at each step. From this preemptive analysis, we will be able to design a mechanism that uses simple inputs to generate this complex motion pattern.

We will also need to consider environmental factors which will affect the conditions the mechanism will be operating under. For the sake of maintaining a repetitive pattern, we will likely establish some consistencies in the environment to simplify the requirements placed on the mechanism in completing its task. We will also need to consider the relationship we intend to create between the activation and output of simple electrical components and their subsequent input to the mechanical system of bodies and linkages. The method of converting this input energy into different types of motion will require multiple types of component bodies included in the linkages.

It would be interesting to adapt this system to more environmental applications. Varying the final position in the pattern is one way of doing this as well as varying the size and weight of the water bottle itself (empty) that can be used. Another interesting way of expanding upon the system would be to implement it such that it works in multiple environments (a car, a desk, the floor).