User:Medelen8/ENES100/Bionic Tripod Design

Problem Statement
The find an easier and very efficient way for the disabled and/or the elderly to get everyday household objects that may seem easy to collect for people who have no disabilities. The problem is that this class of people are finding it very difficult to reach or even get things around them without having to seek some sort of aid or use a wheelchair. Lets take a look at some scenarios;

(i) The TV remote controller mistakenly falls on the floor and rolls away a distance such that the person must stand up from the couch

(ii) The phone is ringing and I want to get the phone from the table without having to reach over and strain the the body of someone with a bad back;

These household issues face these disabled/elderly people regularly and picking it up is easy but yet so difficult, thats where the bionic tripod comes in. Bionic tripods are built mainly for industrial and laboratory use, but we aim to design a bionic tripod to meet the needs of these class of people. Some of these questions arise;

Is it Efficient?

Is it User-friendly?

Does it appeal to the target consumers?

Is it cheap?

and most important of all, does it solve the problem at hand?

At the end of the Implement Phase, only when we get a yes to all these questions do we determine that the project has been a success.

Requirements for each element or component derived from system level goals and requirements
The system goals and requirements are as follows

1. pick up any object of size ranging from a ping-pong ball up to an average sized orange. (3inch diameter) weight is limited to 2 pounds.

2. grip objects strong enough to hold object for prolonged periods of time (15-20 seconds)

3. need to move objects from point A to point B, point B can be anywhere up to 2 cubic feet from point A.

4. gripper must be able to hold sturdy objects as well as fragile objects (must be able to control strength of grip)

5. need to maneuver around minor obstacles.

6. Must cost not more than $200

Requirements 1,2 and 4 apply to the gripper (claw) specifically, while requirements 3 and 5 apply to the arm.

In addition to the requirements above, the tripod will, at the end of the implement process, have a "test" to ensure that all of the requirements have been met.

This 3 minute timed test will have several challenges that need to be "cleared" for it to pass the test.

-move 1 apple, 1 egg and 1 orange from point A to point B in 2 minutes time. Point A and B are no more than 2 feet apart within each other.

-*The arm cannot drop the object or do significant damage to the object

Concept 1:
The first concept was to have two gears of the exact dimensions, which would serve as an open and close mechanism for the claw and would be powered by two motors for each gear as opposed to one, to give better torque and ultimately a wider weight and size range of objects that can be picked up. The claw in this case is going to be plastic and printed using a maker bot, and the inner part will be coated with rubber to give better grip on objects. The motors in this case would be powered by an Arduino which would be located at the far end of the robotic arm, away from the claw. A 2mm diameter cable would transfer power from the Arduino to the motors which open and close the claw. The cable would be arranged in such a way as not to have wires hanging all over the place. This is key because our main priority is to come up with the best possible design with the available materials. We decided not to go with this idea because having to position two motors at the wrist of the arm where the claw is was going to make the whole arm wrist-heavy and therefore wasn't very effective.

Concept 2:
The second idea is to use a 3D printed plastic claw as well, but this time, the claw will have tiny holes with which high tension rubber bands would be passed through and connected to a motor. Also, this time, the motor would be placed at the far end of the robotic arm, away from the claw. The motor's clockwise or anticlockwise motion would act as a pulley that opens and closes the claw. The arm will be controlled by actuators sliding on a metal rail. This is similar to the final design but the difference is that we only had one base which had both the motors that would be controlling the claw and also the actuators making the base have too many devices making it a logistical nightmare to figure out how to arrange everything so they perform their functions effectively.

Concept 3:
Concept 3 was born from watching a video of an elephant trunk. From observing an elephant trunk, we saw how it was flexible and pliable yet strong and sturdy. Festo's "Bionic handling assistant" seemed to be inspired by the elephant trunk as well. We began by seeking out everyday materials that resemble an elephant's trunk. We imagined a vacuum hose line that can be commonly found in a house hold vacuum cleaner and tried to make our own version of this arm by combining the ideas that we already mentioned from concept 1 and 2. The 3 limbs of the trunk would each be powered by sliding actuators that control the movement of the limbs. At the claw end, the 3 limbs would attach to a metal plate that connects the 3 limbs into one joint. The movement of the claw is the same as concepts 1 and 2.

Video of Elephant Trunk

The initial design
The initial design was created by the people that started working on this before us. They came of with a working model and design for this tripod. We created a design that would improve the overall movement to make it smoother. The initial design was sound and had a good base we could work off, but we decided to go another route with the design because we set new goals and constraints and the initial design just won't meet our goals EFFECTIVELY. The initial design made use of a carton box which we felt could be improved and also the design of the claw. Below is the overview of the previous design and what was achieved within the project life-cycle.

https://en.wikiversity.org/wiki/Robot_arm/Howard_Community_College/Fall2011/502_TFCW https://en.wikiversity.org/wiki/Robot_arm/Howard_Community_College/Fall2011/502_TFCWNS

Experimental prototypes and testing conducted during design
Not Applicable

Appropriate optimization in the presence of constraints
Some of the constraints on this project was to have the bionic tripod move the required objects within a specific time frame. Objects that should not weigh more than 3 pounds, and the object should be moved a distance of 2 feet within 15 seconds maximum. Our initial design was to have a series of gears at the wrist area of the arm which would be able to open the claw very effectively because of its proximity (distance) to the claw. At some point, this concept looked the best, but to be able to overcome a load of about 3 pounds, the arm-hand area was very front-heavy and would not effectively carry out the required task in 15 seconds, so we had to do a bit of reverse-engineering. we decided to put the main moving mechanism at the other end of the device. This would be able to overcome a load of 3 pounds but the increased distance now meant the task could still not be completed within 15 seconds so we decided to use two(2) 12V motors which give more power therefore would open and close the claws faster, and subsequently complete the task within the required time frame. Another constaint was that the device couldnt cost more than $200, so we decided to use cheap steel sheet metals and would do the welding ourselves to save costs of having an external party do the welding and integration of some parts. We were able to optimize efficiently with the constraints present mainly by brainstorming and analyzing every decision to be made, even decisions as little as deciding what color we wanted to paint the exterior part.

The final design
The Final Design took about three(3) weeks to be finalized. Mainly because we could not agree on the kind of motion to incorporate into the movement of the claw. This design was done based on a decision matrix, and group discussions on the route to go with component parts.

Components

Metal Supports (Steel)

The decision to use metal supports to support the main unit was an automatic one. Steel is very strong and cheap, and will guarantee the long-term strength of the unit. The steel supports are going to stand erect at a distance of about 1.5 feet from each other. Bolted and welded to these supports will be the 'diamond box' which contains the wires and actuators which move some other components that will be discussed below. Also bolted to these metal supports at the upper level,is a steel base about 2mm thick. This base will serve as a platform where the two(2) arduinos will be placed. It will also serve as a permanent location for the motors and gears that will open and close the claw. These metal supports ideally should be about 5 feet long to be able to accommodate all its sub-components. The metal supports are to be made into a rectangular shape open on the two(2) longest sides (similar to the external casing of the Central Processing Unit (CPU) of a desktop computer).

Motors and Gears

Every moving component of this design is by means of a motor. For this reason, it is important to get the appropriate motors for the kind of components to be moved. The motors moving the claws should both be 5V or higher motor because despite the fact that the claws would be plastic and do not require much effort to manipulate, the motors also have to overcome the load of whichever object the claw has in its grasp. We want to be confident that the claw will hold the object firmly and for this reason we require the motor to be slightly more powerful. The motors will be placed side by side on the upper steel base and would be attached together by two gears. These two(2) gears should be the same diameter and have the same number of teeth because in this case, no one gear is driving the other, they are serving similar purposes and exact the same forces in both the clockwise and anti-clockwise directions. So the Velocity Ratio (VR) should be 1 to keep forces balanced. (V.R.)=number of teeth on gear A/number of teeth on gear B. The gears in this design adequately should be plastic because it is light and plastic generate less heat than metallic gears during friction.

https://upload.wikimedia.org/wikipedia/commons/e/ed/Anim_engrenages_helicoidaux.gif

Plastic Claw

There will be two(2) claws as seen in the image. The Claw will be made of plastic printed from a makerbot. We decided to go with plastic because of its lightness, cost-efficiency and also relative size of objects to be carried. The plastic is going to be coated on the inner side with rubber for better grip of objects and it will generally have a round shape to keep objects firmly in its grasp. The claws' motion is going to be controlled primarily by a piston and series of braces as shown in the image. A string split into two(2) at the bottom is going to be attached at the vertex of the claw to allow for maximum range of opening and closing. The string is going to be attached as seen in the image. The claw is required to have a maximum diameter range of 3.5 inches to allow it accommodate the maximum size range of objects for the unit.

Aluminium Rods

The arm component is going to be made up of three(3) aluminium rods with aluminium beams at intersections to provide support and stability during movement. We decided to use Aluminium over Steel because however strong steel is, Aluminium is much lighter and poses very little chance of rust because when the Aluminium reacts with oxygen in air, it forms an Aluminium Oxide which serves as a rust resistant shield. These rods must be very flexible to allow for effective movement in all axis. When you have an arm unit that is very stiffly welded together and not very flexible, movement will happen strictly in just four axis (up, down, left and right), but in contrast, we want to achieve a more 3-dimensional axis of motion for the arm and to achieve this, the rods have to be fairly flexible. The three(3) rods are going to be attached to three(3) metal clamps respectively which would be on a metal rail moving in a linear direction to manipulate the movements of the arm. The rods are going to have LED's woven round them for aesthetic purposes.

The Diamond Box

We call this the diamond box because this is the main brain unit of the Bionic tripod and more obvious, shaped like a diamond. This box contains three(3) Mechanical Linear Actuators or more commonly called Linear Slide Actuators. This type of actuator operates by converting rotary motion to linear motion. The rotary motion of a motor is converted into linear motion using a series of jack screws and or gears. In our design we would be using the actuator that converts the rotary motion of a 5-10V Motor into a sliding (linear) movement of the actuator. Three (3) metal clamps into which an aluminium rod will be attached to each clamp as shown in the image. An arduino and a motor shield will control each motor that drives the Linear actuator mechanism. This will be housed in the diamond box. This diamond box will have three(3) actuators each with a rail along which they move. Notice Rail B is slightly longer than Rails A and C, this is to allow for a wider range of vertical movement of Rod B which would be the primary controller of the vertical movement of the arm. This diamond box has to be well welded to the steel box because this is the part with the most weight and contains the most delicate parts. The diamond box is required to be welded on all 12 edges (6 edges for the front and rear portion of the box).

Integration of Design Components

As stated earlier, the steel box is going to have 2 bases, one above the other. The lower base is going to support a diamond shaped box with three rails (one on both sides, and one at the top). these rails are going to serve as a source of linear movement of the three flexible rods (Robotic Arm).The rods are attached to metal clamps respectively. It is these clamps that will convert linear motion to the vertical and horizontal movements of the arm(four (4) Axis).These clamps are connected to actuators which will be powered up by Arduinos. If clamp A moves forward (towards the viewer of the drawing), it pushes rod A, which in turn moves the whole arm to the right. If clamp B moves forward, it pushes rod B, which moves the arm to the left. If Clamp A is moved forward to its limit of movement and Clamp C backward to its limit of movement, the arm will achieve its maximum horizontal range to the right. If Clamp A is then moved backward to its limit of movement and Clamp C forward to its limit of movement, the arm will then achieve its maximum horizontal range to the left. The total range of movement, both left and right would effectively be 2 feet. Rail B will have a much longer rail, hence a longer range of motion because, when clamp B is moved backwards to its full range of motion, the arm then lifts up. Because more effort (e) is required to lift the arm when a load (L) has been suspended from it(the load being the object to be lifted and moved), the actuator on clamp B is going to require more power than actuators A and C. Coming to the claw, from the drawing, we can see that a string has been labelled. This string will be attached and woven around rod B and connected to two (2) gears located on the upper base along with the Arduinos and other power sources and cables. The string has two ends woven around the gears like a pulley. When the motors move the gears in the opposite directions such that, the gear on the left moves in an anti-clockwise direction, and the gear on the right moves in a clockwise direction, the resulting movement functions like a pulley system which pulls the string upward. The string, which is attached to both claws, is pulled up and ultimately, this movement opens the claw up. When the gears then move in opposite directions again such that the gear on the left moves in a clockwise direction and the gear on the right moves in an anti-clockwise direction, the resulting motion pushes the string down, subsequently closing the claw back up.



Technical and scientific knowledge
To efficiently design the tripod arm, we used our basic knowledge of physics and mechanics. First, we contemplated the forces that would act on each component of the arm. If we utilized a horizontal design, we would have to account for the effects of gravity (g=-9.8 meters/s2) on either one or two of the cables of the arm. This would make coding more difficult, since the motor speed when moving away from the ground would have to be greater than when moving down. Similarly,an Arduino Uno can only supply 5 volts of power, give or take small variances. This will be nowhere near enough to power 4 motors which are tasked with lifting a tripod arm and an object

Similarly, we had to use our previous knowledge of engineering to decide on an appropriate material to use for the arm design. After researching different types of plastics and metals,and the structural capabilities of each, we decided on using flexible aluminium rods for the movement of the arm. This is due to the fact that aluminum is generally lighter and has a lower density than most of its metallic counterparts.

Creativity, problem solving, and group decision-making


We began the project by looking at previous designs and group works. We then tried to improve upon those ideas. However, When we decided to start from scratch, creativity was very important. One biggest change that our group made compared to the previous group was to re-orient the arm so that it is laying on it's side rather than hanging from the top like the previous group. We got this idea from looking at our own arm and saw that it was oriented from it's side as well.

One of the problems that we came across was the materials of the claw. There were several opposing ideas that each of the group members argued about. We decided to use the weighted Pugh decision chart. We all knew that the cost was the most important factor, but the real important factor was the strength of the claw because if the claw doesn't have strength and cannot hold anything in it's grasp, the claw would be useless. Seeing the results, the decision was clear.

Prior work in the field, standardization and reuse of designs (including reverse engineering and redesign)
Not applicable

Modeling and/or Simulation
Not Applicable

Performance, life cycle cost and value
As a group we determined the possibilities and how a robot arm could be used. We came up the concept of how this design could help people who have disabilities. This bionic tripod should perform well for those who try to use it. It should be able to move and operate in a wide range of motion (3D Axis). All models must follow the requirements stated earlier.It will operate automatically with a control system (remote controller) to be optimized in the implement phase. The concept that we came up with was a possible design that would promote a more fluid motion than the previous design.

The life cycle of this entire set is that it should last a lifetime. Depending on the age of the software and some of the materials you may want to replace over time, there would be specifications on life cycle of components and when they are due to be replaced. It should be strong and durable. The arm and claw should last a lifetime depending on how well it is taken care of. Judging by the fact that this is targeted at the elderly, it tends to be taken care of quite well by such people. The entire unit should be kept inside so it wont be affected by the external environmental elements such as rain, air, dust etc. Kids below age 5 should not be allowed to operate the device as the movement can cause injury. Maintenance obviously is very important because, like every device or machine we use in our society today, poor maintenance leads to reduced life-cycle. If you get a smaller scale of the robotic tripod you most likely wont have to keep up maintenance as much. On a large scale of this object you would need bigger parts and the possibilities of needing to replace things due to the great usage you may get out of it.

The value of a bionic tripod could vary due to many factors. If you want the best of the best tripod with all the hi-tech and over the edge materials this tripod design could range from a few hundred dollars to a couple thousand. Our bionic tripod is going to cost nothing more than $200 which is quite moderate compared to the range of parts and technical know-how it takes to build the entire unit.

Aesthetics and human factors
A bionic Tripod is most likely to be used in a laboratory, but our bionic tripod is also required to serve domestic purposes in the house. The unit is supposed to appeal to the elderly and/or disabled, so it was important to include a bit of aesthetics. we have decided to wire a series of LED's within the arm. Green and red bulbs would be used to give a Christmas tree effect. This may not appeal to all users so these LED's can be turned off on the flick of a switch. Also the steel casing and supports are going to be painted with colors ranging from Black, Grey, or White. It was important to develop a very important Human-System interface especially because the users we intend to Sell this product tend to be more of the elderly, and we know the elderly do not like user unfriendly systems, therefore the importance of developing a very effective but at the same time a very easy to use control. A remote control system with sensors like that of a Television will have a simple up, down, left and right control like that of a PlayStation analog control stick. For example when the stick is flicked up, sensors tell the actuator B to move backwards fully, thereby lifting the arm up. Also a stick will control the claw. This would have a simple left and right range. For example, when the claw stick is flicked to the left, sensors tell the motors on the upper base to to move in opposite directions so as to wind up the strings and open up the claw subsequently. It is up to the implementors to decide how they want to integrate the systems, but the ground work is already a solid one they can work off.

Implementation, verification, test and environmental sustainability
Our group will make sure to implement by putting the machine to a rigorous test as mentioned in the first part of the report. This test will give us an idea of how the tripod will do in a real world task situation. It will also reveal weaknesses that the tripod may possess and with that, the group can work on eliminating those weaknesses. We are expecting a moderate amount of weaknesses because this will be the first time testing our design. The tripod will be commercially used only after passing the test.

environmental sustainability does not apply to our project because it is purely mechanic and will not interact with the organic world.

Maintainability, reliability, and safety
Our tripod will need medium to minimal maintainance. The motors and actuators are made to last the lifetime of the machine while the arms and claw will need replacement once or twice a year depending on the frequency of use. The actuators will need lubrication once a year to prevent from rubbing against it's tracks. The moving parts of the arm will need protection when applied into the household because unlike a factory setting, there will be hazardous objects around the house that can potentially damage the arms such as pets, liquid or other heavy objects that can fall on the machine. In order to prevent this type of damage, the arms can be covered by a cloth sleeve designed to fit the arm without affecting the range of motion.

The Tripod will need to be used with parental care if used by minors due to the fact that the claw can essentially be used for any task that the user sees fit. Improper use of the arm can lead to serious accidents and physical damage.

Robustness, evolution, product improvement and retirement
Because the Tripod was not initially designed to be used outdoors, it is prone to physical and mechanical damage.

The tripod can be evolved in endless ways. The arm can possibly be used as a prosthetic limb for someone who can lost an arm. Conversely, it can also be evolved into a defense weapon that can detect movement and eliminate enemy forces. The arm is a very basic platform that can be used as a base to build almost anything.

There are still numerous aspects which can be improved upon such as robustness, maintainability, movement of the base just to name a few. This project could be a good starting base for many other projects and inventions.