Mech Design @cleverorchaoticdesign - Tumblr Blog

Our verification and validation

Validation and Verification

Verification, which establishes whether the device design described by the design output conforms to the requirements described by the design input.

Validation, which establishes whether the product produced in accordance to the design output, actually satisfies the user's’ needs.

Validation

“He returns to his bed to sit down as it is impossible for him to reach down and balance on his feet while standing. Carol sits and lurches his back over so his arms are close enough to the floor and where he can position the sock; he needs to position the sock right in front of his foot so he can make sure it goes in right. He ensures the heel is facing the ground and grasps both sides of the sock to spread an entry hole large enough for his foot. Carol proceeds to pull the sock around his foot, his coordination isn’t what it used to be; resulting in his toes catching multiple times upon entry. Carol finds it hard to get a strong grip on the sock and often slips or must let go forcing him to stretch his arms down again and contort his body to reach his foot. When he finally gets the sock on he pulls on the sides to make sure it fits correctly, this is particularly difficult as he cannot manoeuvre his arms so easily.”

With using our design the User still has some control via sliding their foot in the head. This, as well as, the fact the whole process takes less time than before, due to automation, gives the User their independence. This is something that is not really talked about in the requirements but is so important for aging people to have! I am glad we could enable them to have independents. There is now no need to account for 5 minutes of putting on socks in their daily routine and they can go live live to the fullest rather than fluffing around.

We have made deliberate decisions to ensure the comfortability of the User throughout the whole process with having them sit during the process to the curved edges of the head/ foot rest. Comfortability will also be important in the detailed design - with material consideration. The User no longer needs to bend and strain their back but can now sit down and merely add a sock to the device and control the device using a remote - then device moves away.

Failure Mode Effect Analysis

flamingoutcast-blog

Control, and automation

This will just be a brief post but I thought it would be good to talk about the different steps of operation of our final design.

This mainly outlines all of the steps the machine will have to undertake along with the points at which the user will have to have input. We decided a simple remote with On/off, Start, and height buttons would be best to control this process. For any stage in bold to progress to the next(except on) start must be pressed.

General process:

Initial input Move off changing pad (pad one) Locate base pad (pad two) Stabilise Wait for input (ready state) Secondary input (lift) Machine lifts up User puts sock on machine Wait for input (height- up to 500mm) Third input Machine moves down and holds position User lifts foot Machine analysis of angles Machine adjusts User inserts foot Machine slides beads Machine feels resistance (20N) Machine moves away from the foot (minimum clearance of 50mm) Machine waits for input (new sock or OFF) Another foot: Repeats process from second input Finished: Moves down to ready state Disconnects of base pad 2 Moves to changing pad (pad one)

Hand remote buttons are: START LOW MID HIGH (3 height options) OFF

This was intentionally extensive to show how much the robot would be doing alongside how little input would be required from the user. If any stage is left idle for 5 minutes or longer the machine will turn off and return to the charging pad.

cleverorchaoticdesign

We thought the most appropriate style of software architecture to use for our design is the “Client server” style. There would be two micro-controllers in the system acting as individual servers. One micro-controller to control the servo’s in the Arm and the pressure sensor and LDR’s in the Head of the design. A Separate micro controller to control the Roomba function.

Sensors

We often thought about the automation of our device. When we talked about what we wanted it to do it was obvious we would need some sensors.

To figure out what sensors we would need i felt it helpful to write out some pseudo code for how i’d like the design to operate

I will refer to our design as the machine in this case.

The user is seated

The User calls the machine to users position with the remote

The machine’s Roomba function triangulates and moves to users position.

Once stationary at users position Roomba stops and raises its wheels the machine raises the head ready to receive a sock

User places sock over the head

The machine lowers its head to ground level

User places foot inside the head

The sock is rolled and pushed onto the users foot

User removes foot

The machine raises it’s head to receive 2nd sock, the process is repeated until the second sock is on the users foot

After application of second sock and the users foot is removed the machine retreats away from the users position.

Going through the list i can pin point places where sensors would be required

1. The machine triangulates to the users position: to do this the Roomba base will require an infrared sensor in its base and it would likely need to be a medium range High sensitivity sensor

2. User places sock over the head: To increase automation we will require that the machine knows when a sock is placed over its head. To do this we can use a number of LDR’s ( Light dependent resistors) encircling the head. It will need to be quite sensitive so socks with thin fabric will register.

3. User places foot inside the head: This is the reason i added the pressure sensor in the head, the machine will then know when a users foot is inside it so it can automatically activate and put the sock on. It will also know when the foot is removed so then it can get ready to receive the next sock or move out of the users way. The pressure sensor can also measure the forces experienced by the foot which is good for safety and data collection purposes.

With these in mind we were able to add them to our embodiment design!

flamingoutcast-blog

Roomba in the house! Ambitious Steps

One Important thing that I have forgotten to touch on as of yet is the Roomba base. We are highly pulling from the Roomba design(cross section visible below) and just adapting the wheel exchange so there are four retractable wheels for stability.

The Roomba Design is very intricate and the vacuum sections in yellow would be replaced with the mechanisms for the rotating arm. Other than these changes however the design would stay pretty much the same this is due to the ability of the Roomba to find its own way around the room with an infrared reciever.

Similarly we talked about the design being able to find its own way between a charging Pad and an operational pad one where it can wirelessly charge and the other set-up in an ideal position so that the user can comfortably use it. While this is a cool concept however we are unsure of how we will be able to ensure it follows the same path every time and so instead are unsure if any technology currently would be sufficient to perform this task. However what we ideally imagine are an infrared receiver on the design that allow it to find and easily locate the operations pad and then when operations are finished; the charging pad. This sensor would effectively have to be of medium range and high sensitivity in order to accurately find the location of these pads.

The one other thing I felt important to bring up was how we are planning on stopping the design from moving. This is highly based around the concept of a shower mat; either with small suction cups or even just a rubber material it would be able to lower down onto the operational pad similarly made of a rubber material and this would create high friction and stop lateral movement. This is ideal as when pressure is applied to rubber surfaces they become harder to separate keeping everything stable.

cleverorchaoticdesign

Sean has done a great job into researching the Roomba, we can see it is a very viable design to introduce into our concepts!

Our Embodiment Design

We have finished our embodiment design and Sean was nice enough to draw it up all nicely for us

The base uses existing technology based off a Roomba, it is able to navigate itself around and can return to a charging port by itself.

The Arm is controlled by servo motors using gears and screw windings, these give good torque and control on the mechanical arm.

isometric view of the arm and birds eye view.

Design process so far

So far the conceptual design process has followed the general kind of “waterfall” method. The waterfall method is supposed to be good for streamlining idea’s and this design process worked well during the conceptual design stage as we weren’t trying to hard to make the perfect design, making sure it performed all the necessary functions in the best way possible. It did take a while to get all of our concepts together and to then complete the Harris Profile mainly because it was a tricky task to figure out multiple ways to get the sock on a foot!

Once the Harris profile was completed our productivity really increased, we have narrowed in a lot better on what sort of design we are going to do. We are headed towards getting our embodiment design. The concept we have so far is still kind of ambiguous and broad.

Each piece, the head, the arm and the base, still need further development. We will focus on the 3 embodiment design goals. Gaining clarity by maintaining clear functions. Maintaining simplicity and safety.

We have had frequent design team meetings and our design process has very much changed to a “Iterative and incremental development” design process. We continue iterate over previous designs as we develop our embodiment design.

Things such as adding sensors, ensuring we account for possible modes of failure, and have the design abide by all the Design Specification test criterion all requires iteration and each time we are sure to check our Design Structure Matrix for any other design changes that need to be done elsewhere.

----------Click the GIF to see a rough simulation of the beads in action!------------

This is a cutaway view from the top of the device, as i push the beads forward the thick white string represents the sock folding around the foot.

My final concept contribution

Developing the Head.

The beads method needed to be tested so we came up with a prototype to demonstrate whether it would work or not.

Click the image in the post above this one to see it working

Proof! the beads have a good chance of working!

However I realized there was a potential mode of failure.

This picture demonstrates that in the second step and as seen in the previous posted video, that at the time when the sock is going around the heel on the bottom of the foot it travels a larger distance than the part of the sock that is on top of the foot. As the beads are all traveling at the same speed and covering the same distance this would mean the sock would not go all the way around the heel and up the ankle before the top part of the sock is fully rolled out.

I found a solution to counter balance this design flaw. The beads travel half the distance than the piece that pushes them because the beads have to fold in half back on themselves. If a couple rod’s ( that do not double back on themselves) are fitted on the bottom we could push the sock up and around the heel quicker whilst only rolling the top part of the sock a little way up the foot. These rods would be made from a strong and flexible “Shape-Memory-Alloy” that would remember its shape enabling it to curve up and around the heel.

I also thought that if the beads were held in place by railings either side of the beads then the apex of the beads would actually protrude above these railings. The beads would then also drag the sock along ever so slightly when they are being pushed forward mitigating some of the frictional forces created by the constricting sock on the outside sleeve.

my finished concept solution for the head piece which holds, inserts and guides the sock over the foot too.

The shaded area at the back of the sleeve represents a pressure pad sensor that detects when the users foot is in place inside the device and when it is removed. This helps add to the non-functional requirements as it is safely activated and deactivated by the users foot and can measure the pressure applied to the foot. Making it activated by the foot also increases autonomy and increases the speed of the operation, the foot activates the device automatically when it is inserted into the head.

Here is my final concept design of the head.

I added little rollers between the rods for comfort reasons so they would roll smoothly under the users foot and around the heal.

Developing our Embodiment

From the Harris profile we chose the pieces best to develop.

The “Head” of the final concept design was to be based on and developed from the head of my concept design. We thought the beads were a viable solution going off our gut-feeling. Also the “Arm” was chosen to be developed from my concept. The Roomba style base with its superior stability and maneuverability was chosen from Sven’s concept.

We decided we would each go away and further develop a piece of the embodiment design each.

I would do the head. Mitchell and Sean would do the mechanical arm as it was quite complex with it requiring servos, gearing and varying degrees of movement. Sven would do the base and Monique would start looking at the software and developing some pseudo-code for it.

Comparing our concepts

We start with absolute evaluation to eliminate concepts. We chose from the group 3 concepts to compare, the aim was to then choose one design to develop. To do this we used a method that Sven endorsed called a Harris Profile which is a type of relative evaluation where we will compare different criteria of the 3 concepts against each other and then rate them on the basis of our gut feeling.

The first concept chosen was Svens.

The second was Monique’s

and the third was mine

this is a rough sketch i quickly did before we did the Harris Profile as i didn’t actually have a drawing of the base, arm, and head combined, you can see the 3 on it as it was the 3rd choice, how authentic.

Here’s our Harris Profile results!

my design performed well on extension, adjustability, size, freedom of movement, speed and weight.

At the conclusion of this meeting we decided that because there was not one single best design, but that some designs were better at things than the other, that we would simply take the best parts of each design and then combine them together in order to develop our final concept solution.

My finished Concept Design

Alright so i still need a bit of functionality

Adjust to angles

Adjust to heights - The system must be accessible up to 500mm from the floor to allow for use at different heights.

Move clear - A minimum clearance of 50mm in all directions (with the only exception being the ground) must be maintained from the position that the sock was inserted.

Stable - When the system is in operation it must be able to withstand: -300 Newtons statically loaded while the user is seated.

Maneuverable - The system will be able to be placed and moved around the house hold with little effort, have a method of moving the system without having to lift it, and be small enough to fit through doorways.

I tried to hit all of these last functions at once in one quick design! ill be honest i didn’t put as much thought into accomplishing these as i did on the previous concept designs because i was short on time but that’s ok! i combined parts from the morph chart to tick all the boxes and hopefully the other guys will have some nice concept designs and perhaps simpler is better haha. At the end of the process i did a quick Go/NO-Go screening to make sure my finished concept design had all the neccessary functions to acheive the system requirements.

e.g is it manouverable? yes, is it adjustable to different heights? yes, etc.

Here’s my concept

see it adjust to angles with its 3 joints with varying degrees of movement!

see it adjust to heights with its collapsible and extendable arm!

see with the arm design and wheels it can move clear! AND is maneuverable!

see with its large base it is stable!

here’s the parts i took from the chart, the rest added myself.

Concept Design - part 2

I decided a hard plastic frame that the sock would fold around would be best for thee head as it would most easily resist the constrictive forces of the sock. However thinking of beads gave me another idea. Perhaps i could use them to guide the sock on, here’s why:

First here’s a short video, its to demonstrate that when the sock is rolled up enough (or folded back enough) the foot can easily slip into the end of the sock, no guidance is needed.

however getting around the heel and up the ankle is trickier

We found there are 3 steps to how most people put on socks.

Toes in

Around the heel

Up the ankle.

So i needed to replicate this movement in order to get the sock on.

Getting the toes in is the easy part. If the sock is held open in a way that the ends are rolled up or folded back over the head then we can simply slip the toes in to the first part of the sock.

Getting the sock over the heel. Sven came up with a good concept here

We can see he designed a cup like shape. The sock is inserted into the cup and then folded back around the outside of the cup. The first part is inserted into the sock, and then to achieve the second part of getting the sock over the heel he has made a flap that would flick it around the heel.

I was inspired by this idea however i feared that when the flap got to the point where it was perpendicular to the heel then the sock would slip down and become jammed into the hinge of the flap. If that was not the case and perhaps the sock was fixed to the flap in some way then the flat would end up stretching the sock much to wide anyway.

I remembered the property of beads - that they will roll over each other when pushed and perhaps this method could be used to roll the sock along the heel and then up, avoiding stretching the sock.

so i came up with this concept. To have beads run along inside the cup shape and then these beads could be pushed forward which would then push the sock from underneath the fold and roll the sock up the foot.

concept sketches:

The beads are pushed out and will roll the sock up the foot.

SO! that’s the tricky part of my design completed and the HOLD OPEN, INSERT and GUIDE ON functions of the morph chart completed.

now to complete the rest of my concept!

functions left to add to my design are:

Adjust to angles

Adjust to heights

Move clear

Stable

Maneuverable

My Concept Design - part 1

Here is my concept design process. All the constituent pieces were gathered from the morph chat and i also added my own little adjustments when necessary, my end concept will contain all the individual functions.

Our morph chart:

With our new design parameters in mind we aim to only don the sock, so the key functions my concept design needs to perform is:

Hold open

Adjust to angles

Adjust to heights

Insert ( the foot must be able to be inserted)

Guide on

Move clear

Stable

Maneuverable

I spend most of my time developing the part of the design that would hold and don the sock because i felt this would be the trickiest part to achieve. I will refer to this piece as the “head“ of the design. I liked the open ended tube design that we had prototyped so i chose to select that part from the morph chart and develop that idea further. The sock didn’t slide so easily over Monique foot but there was plenty of room for improvement. The head is the part of the design that holds open the sock with a foot needed to be able to be inserted into it.

Some rough initial sketches: very similar to the sock slider in the video i posted earlier.

Remember the insight; i wanted it to receive the shape of a foot. So it needed to be less round, flat, almost oval.

Here i started thinking of a beaded bracelet, the properties of the beads and elastic could take the shape for the tube that i desired. If i could get it to hold open a sock - it having a limit where it cannot be constricted smaller by the sock BUT also having the property where it could stretch bigger for when the foot is inserted then that would be a very practical solution.

A half circle would stretch a sock much less than a full circle while still being strong to resist the constrictive forces of the sock! and still a very similar shape to a foot!

Here is an even flatter design with smoother edges to allow the sock to easily slide over. However it would be a hard plastic in this case.

I thought perhaps it could be adjustable too, why not? and have little wheels on the edges to help guide the sock.

Forgoing the “remove sock function” - another kind of insight

When coming up with overall concept solutions from our morph chart - having a design that both dons and doffs a sock, it became increasingly obvious that we could not design a product that would both don and doff a sock itself but instead it would take two individual product designs - one to don the sock, one to doff the sock combined in a system to achieve our SSoN and user requirements.

If our design is not one complete thing but simply two things working together then we need to re-assess if it is necessary to have both.

When we did our modelling to gain insights into our concept designs we also prototyped ways to remove a sock. The one that worked most effectively and simply was nothing but the toilet brush handle pushed down the back of the leg, slipping the foot out and pushing the sock off the foot at the same time ( much like a shoe horn). We also fixed a hook to the end of the toilet brush handle and found it easy to pull the sock off that way too.

We decided as a group to go in a slightly different direction for our design. When once our designs purpose was to don AND doff a sock we would just focus on the donning of the sock. It does not make sense to have two separate products and the removal off the sock can be done very simply by anyone with a long enough stick.

Donning the sock is what the target users most struggle with so we will design just for this purpose from here on out.

We also removed the requirement that the device should be able to be used whilst standing up, while it still could be used standing up it is no longer a requirement.

The User requirements that this takes out of play are:

- The user must be able to doff sock.

and the System requirements are:

- The system must be able to grasp a sock that is already on a foot.

- The system must guide a sock during removal for the socks full length.

- The system must move clear of the foot once the sock has been removed.

- The system should allow easy access to the sock once it is removed.

and the test criterion this affects:

- While the system is in operation it must be able to withstand -700 Newtons statically loaded while the user is standing.

This was voted on and is in the best interest of the team to provide an efficient product within the time constraints.

The insights

When i got home i pondered on a few things and had some realizations.

Firstly i was surprised at the force it took me to pull the sock over the round mouth of the sock holder piece. I thought “why is it so strong?” well that was because we stretched it so much! then i thought “damn how can we stretch it less we need to get a large hole so the foot will fit in”. It wasn’t actually for a week or so more that i realized... hold on! a foot isn’t round! we don’t need to stretch it into a round shape, we need to stretch it into the shape of a foot! So what shape is a foot?

Well it was this weird kind of flat lumpy cylindrical rectangular shape. If we deign the sock holder to be this shape then it’ll stretch less but still be open enough to accept a foot. Ill remember this on my concept designs.

Next i was surprised that when the sock was on the sock holder just how much force the sock applied to it. A stretched sock actually does have quite a lot of constrictive force behind it. I had to pull the plastic apart on the toilet brush holder as it was only very thin.

This other we concept we prototyped didn’t work well at all for that reason exactly!

The clips were to pull open the sock, for it to work they would need to pull with quite a lot of force! The sock holder piece would have to be sturdy and strong in order to counter the constrictive forces of the sock.

Next it seemed the design actually held some promise too. We managed to get the sock a fair way over Monique foot but then a certain way down the pointy edges of the sock holder piece began to cut into the fabric a great deal and stopped the sock from sliding further.

I realized it would have to have smooth edges and be frictionless to help the sock slide of the sock holder and onto the foot.

Gaining insights through modelling

We now had a lot of ideas through our morph chart in order for us to develop some concept designs. We were to go away as individuals and put together pieces of the design that we felt would be successful together and then we would comeback together and compare our concepts.

Before/whilst we were doing this we were asked to bring some materials to class in order to construct some rough prototypes. See this extract from one of Andy’s slides:

Modelling and simulation can also be used in conceptual design as a means to choosing the best idea to take further–This is the focus for the next few weeks

This is not just limited to modelling and simulation, but can include the production of rough and ready prototypes

So we brought some materials.

One of the things i was keen to replicate was the piece specifically that would apply the sock to the foot. I strongly felt that the application of the sock onto the foot would be the most difficult part of our design to achieve.

I had seen a video on the internet of the sock slider, a product already out there than appeared to work.

If there was evidence that this would work then i felt that we could improve on the design.

Here’s pictures of us testing a similar shape that we cut our from a toilet brush holder!

you can see where we made the lines on the toilet brush holder and cut it into shape

We gathered some valuable insights from this modelling and It greatly effected my concept design.

I”ll go into that in the next post.

Trending Blogs

Recently Viewed Blogs

Mech Design