Biomechanical Joint Lesson Plan - Rochester Institute of ... · PDF fileTEAK Biomechanical Joint Lesson Plan Page 2 The TEAK Project ... • Activate devices ... the output force equals

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Rochester Institute of Technology

THE TEAK PROJECT: TRAVELING ENGINEERING ACTIVITY KITS

Biomechanical Joint

Partial support for this project was provided by the National Science Foundation's Course, Curriculum, and Laboratory Improvement (CCLI) program under Award No. 0737462. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

TEAK Biomechanical Joint Lesson Plan Page 2

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ACTIVITY OVERVIEW Biomechanical Joint Kit Overview Students who complete this activity will apply the basic physical concept of mechanical advantage, in combination with information about the way the human body is constructed, to build functioning mechanical arms. The activity illustrates some of the challenges faced by engineers who design and develop mechanical prosthetics, and forces the students to consider design trade-offs. As part of this activity, students will be able to use air muscles, which are engineered components that function in a manner very similar to human muscles.

Activity Time Description

Biomechanical Joint 30 min

During this activity, the students will work in teams to figure out the best way to move a biomechanical elbow. They will learn about mechanical advantage and then use what they learned by trying different attachment positions for the muscle. Finally, students will choose their optimal muscle configuration.

Extension: Air Muscle 10 min

During this activity, the students will learn about the parts that make up an air muscle. They will then get to see an air muscle power the mechanical joint from the above activity. The students will use what they learned and observed about the air muscle to compare and contrast it with a real human muscle.

Learning Objectives By the end of this lesson, students should be able to…

• Explain what bioengineering is • Solve an engineering problem • Weigh pros and cons to determine the best design • Describe what an air muscle is and how it works

NYS Learning Standards Standard 1: Engineering Design

• Will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to pose questions, seek answers and develop solutions.

• Activate devices • Design a structure or environment (e.g., a neighborhood) using modeling materials such as LEGO Duplo

blocks, model vehicles, model structures, etc.) Standard 5: Technological Systems

• Will apply technological knowledge and skills to design, construct, use, and evaluate products and systems to satisfy human and environmental needs.

• Identify and operate familiar systems • Assemble simple systems


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TABLE OF CONTENTS Instructor Preparation Guide .................................................................................................................................. 4

Bioengineering Overview ....................................................................................................................................... 4 Biomechanics Overview ......................................................................................................................................... 4 Mechanical Advantage ........................................................................................................................................... 5 Air Muscles ............................................................................................................................................................. 5

Bioengineering Discussion ....................................................................................................................................... 7 Background Information ......................................................................................................................................... 7 Bioengineering Group Discussion: 5 Minutes ........................................................................................................ 7

Mechanical Joint Activity Introduction ................................................................................................................. 8 Background Information ......................................................................................................................................... 8 Simplified Definition .............................................................................................................................................. 8 Mechanical Elbow Group Discussion .................................................................................................................... 8 Learning Objectives ................................................................................................................................................ 9 Materials ................................................................................................................................................................. 9 Roles ....................................................................................................................................................................... 9 Procedure .............................................................................................................................................................. 10

Mechanical Joint Activity Introduction ............................................................................................................... 13 Background Information ....................................................................................................................................... 13 Simplified Definition ............................................................................................................................................ 13 Air Muscle Group Discussion .............................................................................................................................. 13 Learning Objectives .............................................................................................................................................. 14 Materials ............................................................................................................................................................... 14 Procedure .............................................................................................................................................................. 14

Concluding Discussion ........................................................................................................................................... 15 Mechanical Joint Activity Handout ...................................................................................................................... 16 Mechanical Joint Activity Handout Answers ...................................................................................................... 19 Image Sources ......................................................................................................................................................... 20 Revisions .................................................................................................................................................................. 20

Signifies Group Discussion Signifies Activity


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INSTRUCTOR PREPARATION GUIDE Bioengineering Overview Bioengineering is the use of engineering principles to facilitate challenges in the fields of biology and medicine. Bioengineering applies engineering design principles to model any living systems. Biomechanics Overview Biomechanics is the application of mechanical principles to living organisms. Mechanical engineers apply their engineering principles and knowledge of physics and mechanics to simulate living objects. Areas of biomechanics that will be covered in this lesson include prosthesis, robotics, and materials. Prosthesis helps disabled humans perform tasks that they otherwise could not perform. Robotics is helping doctors perform surgeries that take a great deal of precision and control. The materials needed for these applications of biomechanics must be selected based on the many different functions and environments a system will be used in.

Figure 1 – X-Ray of Human Elbow Figure 2 – Robotic Hand with Air Muscles


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Mechanical Advantage Mechanical advantage is a factor by which a simple machine can multiply an input force to overcome a resistance. Many human joints can move in multiple directions, but for this activity we will be focusing on a simple, one direction of motion joint similar to the elbow. In some cases a human can lift more than 50 lbs alone using just the bicep muscle, even though the mechanical advantage is the least favorable. The three orders of mechanical advantages for a lever are shown on the right. The first order has a mechanical advantage of one, where the output force equals the input force. The second order has a mechanical advantage greater than one, and the third order has a mechanical advantage less than one. MA = Output Force ÷ Input Force The students will be able to experiment with how the mechanical advantage would change if the bicep muscle were located along different points of the forearm. They will be asked to test the different connection points and determine the pros and cons of each scenario. The students will also use different methods to apply a force. This will allow them to act as engineers who are trying to solve a problem by maximizing the effectiveness of a system.

Air Muscles Air muscles are operated by compressed air. They are very lightweight because their main element is a thin membrane, usually made of latex or silicone. This allows them to be directly connected to the structure they power, which is an advantage when considering the replacement of a defective muscle. Since the membrane is connected to rigid endpoints, which introduces tension concentrations and possible membrane ruptures, muscles may need to be replaced on a regular basis. Another advantage of air muscles is their inherent compliant behavior: when a force is exerted on the air muscle, it "gives in" without increasing the force in the actuation. This is an important feature when the air muscle is used as an actuator in a robot that interacts with a human or when delicate operations have to be carried out. In air muscles, the force is not only dependent on air pressure but also on each muscle’s inflation. This is one of the major disadvantages, because the mathematical model that supports the air muscle functionality is a non-linear system which makes them more difficult to control precisely. However, the relationship between force and extension in air muscles mirrors what is seen in the length-tension relationship in biological muscle systems. Another disadvantage is that gas is compressible, so an air muscle that uses long tubes must have a control system that can deal with a delay between the movement control signal and the effective muscle action. An air muscle actuator system needs electric valves and a compressed air generator, both of which are neither light nor small.

Load Fulcrum

Effort

Fulcrum

Effort

Load

Effort

Resistance Fulcrum


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Biomechanical Joint

DURATION 50-55 Minutes

CONCEPTS Bioengineering Biomechanics

Mechanical Advantage Medical Applications


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BIOENGINEERING DISCUSSION Background Information Bioengineering is the application of engineering principles to address challenges in the fields of biology and medicine. Bioengineers are motivated to make breakthroughs on human health while promoting environmental sustainability.

Bioengineering Group Discussion: 5 Minutes (Pose the following questions to the group and let the discussion flow naturally…try to give positive feedback to each child that contributes to the conversation.)

Q: What do you think bio (biology) means?

• The study of life and a branch of the natural sciences that studies living organisms and how they interact with each other and their environment.

• The study of the environment. • The study of living organisms and living systems.

Q: What do you think engineering is? What do you think it means to be an engineer?

• A technical profession that applies skills in: o Math o Science o Technology o Materials o Anatomy o Environmental Studies

Discuss with the students what bioengineering is and the broad scope of areas that bioengineering includes. For this discussion, provide students with examples of bioengineered products and applications.

• Bioengineering applies engineering principles in the fields of medicine, biology, robotics, and any other living system.

• Examples of products that have been bioengineered are: o Prosthetic Joints o Artificial Limbs o Hearing Aids o Artificial Organs – Heart, Lungs, etc. o Dialysis Machines o Contact Lenses


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MECHANICAL JOINT ACTIVITY INTRODUCTION Background Information This kit contains discussions and an activity to help students to gain a better understanding of how engineers solve complex technical problems and design medical instrumentation. It demonstrates some of the issues faced by engineers who design and develop mechanical prosthetics, and allows students work through these issues to construct and test a simple biomechanical elbow joint.

Simplified Definition Mechanical Advantage - A factor by which a mechanism multiples the force. The force you get out divided by the force you put in.

Lever - A simple machine used to lift weight.

Biomechanics - Taking knowledge of mechanical systems and applying them to living organisms. EX: Prosthetic joint, robotics.

Mechanical Elbow Group Discussion (Pose the following questions to the group and let the discussion flow naturally…try to give positive feedback to each child that contributes to the conversation.)

Q: Can you think of an example of a lever?

• Seesaw • Wheelbarrow • Wrench • Bicycle Hand Brake • Your arm

Q: Do you think these levers make it harder or easier to work?

• Easier, because of their mechanical advantage Discuss the 3 orders of levers and draw diagrams on the board

• First Order Lever o The fulcrum is between the effort and the load. Mechanical advantage = 1 o EX: See saw, scissors

• Second Order Lever o The load is between the fulcrum and the effort. MA is greater than 1 o EX: Wheelbarrow

• Third Order Lever o The effort is between the fulcrum and the load. MA is less than 1 o EX: Shovel, your arm!


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Q: If someone needed a mechanical limb (such as an arm), what kind of simple machine should they use? • A lever

Q: Why would someone need a mechanical limb?

• To replace a lost or missing limb • To perform a task that a person cannot do on their own • Increase strength or motion of a human limb

Q: What do engineers need to know to create a mechanical body part?

• Range of motion • Strength • Size • Purpose

Learning Objectives By the end of this exercise, students should be able to…

• Work as a team to build an apparatus • Follow a procedure to test predictions • Analyze data that has been collected

Materials • (1) Activity Worksheet • (1) Mechanical Joint with Quick Release Pin • (1) Clamp • (1) Clip • (1) Ruler • (1) Protractor • (1) Bag of Team Roles

Roles ME Mechanical Engineer – Responsible for setting up the mechanical joint with the assistance of other team members. DE Design Engineer – Responsible for modifying the design features with the assistance of other team members.

TE Test Engineer – Responsible for making the mechanical joint move with the assistance of other team members. DataE Data Engineer – Responsible for collecting and recording data with the assistance of other team members.

Biomechanical Joint Activity – 30 Minutes


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Procedure 1. Have the students get into 5 groups. 2. Draw the First, Second, and Third Order levers from the mechanical advantage schematic on the board and

explain what they mean. (Should have already been done!!) 3. Hand out one activity worksheet to each group. 4. Instruct students to discuss the first three questions with their group and come up with answers. 5. Discuss the questions/answers with the class. Tell them that they will be able to test their hypothesis (what

they think will happen) with the mechanical joint activity. 6. Hand out the joint activity kit.

**Make sure that the students understand that the activity will be done as a group. Each step of the activity will start with verbal instructions and then the students will get to do that part. The instructor should walk between groups to check that everyone understands the instructions and that they are doing the activity correctly. After each step is completed, students should raise their hands to let the instructor know that their group is ready to move on. Demos may be helpful for the assembly and first test. ALL Take ALL of the parts out of the plastic container, and put the container on the floor. Open the bag of team

roles. Place the role tags upside down on the table. Everyone pick a tag and read your team role and the role description.

ME Attach the clamp to the side of a desk/table. To attach the mechanical arm to the clamp, take the end with

the black pulley wheel and put it through the clamp from the bottom (so that the wheel ends up on the top with the arm/joint hanging below it). Tighten the clamp onto the arm so that it holds it securely.

DE Take the quick release pin and put it through the hole in position A (the hole closest to the hinge) on the

mechanical arm. Make sure that you put the pin through from the top, so that the lanyard will be in the right position. Lay the lanyard over the pulley.

TE Make sure that the lanyard is pulled taught, but that the arm is still hanging vertically. Attach the clip to the

lanyard on the side of the lanyard that you are pulling, and make sure that it starts off touching the pulley. ME Take the protractor out. Hold the protractor next to the arm so that the flat side is parallel to the arm. When

the TE starts to pull the arm, you will need to watch the protractor and stop the TE when the arm is at a 90° angle.

TE Start to pull the string and raise the arm until the ME tells you to stop. DataE Use the ruler to measure from the black pulley to the clip on the lanyard. Write down the length of the

lanyard that was used in the appropriate box. ALL Repeat the procedure for the other 3 positions. TE Take out the hanging weight. Hang it from the hook on the end of the arm. DE Move the quick release pin back to position A.


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ALL Take turns moving the arm from its resting position (hanging vertically) to the farthest position it will

move. Think about how hard it is to lift the arm/weight. DE Move the quick release pin to each of the other 3 positions. (Leave the weight in the same spot.) ALL Take turns lifting the weight with the lanyard in each of the other 3 positions. Discuss how hard it was to

lift the arm/weight in each position. Rank the positions on how easy/hard it was to lift the arm and weight assembly. Write the word hard in the box for the position that was the hardest to lift, and the word easy in the box for the position that was the easiest to lift. Draw an arrow from easy to hard. Then have them pick 2 positions and fill out the pros and cons of each muscle setup in the charts provided. They will use the tables to help them pick out the mechanical joint design they think is best.

DataE Write down the hardest and easiest lifting positions that your group decided on. ME Take the mechanical arm out of the clamp and remove the clamp from the desk/table. Put all parts back into

the container. ALL Answer the questions on the bottom of the activity handout. **While the students are working on the concluding questions, collect all the activity kits and check them for parts.

End Biomechanical Joint Activity


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Lesson Extension Activity

DURATION 20-25 Minutes

CONCEPTS Air Muscles


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MECHANICAL JOINT ACTIVITY INTRODUCTION Background Information Air muscles are operated by compressed air. They are very lightweight because their main element is a thin membrane, usually made of latex or silicone. This allows them to be directly connected to the structure they power.

Simplified Definition Air Muscle – A man-made “muscle” that uses air pumped into tubing to mimic the actions of human muscles. It works like a Chinese finger trap.

Air Muscle Group Discussion (Pose the following questions to the group and let the discussion flow naturally…try to give positive feedback to each child that contributes to the conversation.)

Q: What muscles could air muscles replace?

• Any muscle Q: What are some things that could go wrong with an air muscle?

• Hose comes unattached • Clamp loosens • Hook pulls out • Air connection breaks

Q: Would you want to have a human bicep muscle or an air muscle bicep? Why?

• Whatever they think will be correct • Some possible answers:

o Human biceps can lift more than an air muscle o Human biceps don’t need an air source to make them move o Human biceps don’t have parts that need replacement o Human biceps can fix themselves


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Learning Objectives By the end of this exercise, students should be able to…

• Describes what an air muscle is and how it works • Determine similarities/differences between an air muscle and a human muscle

Materials • (1) Mechanical Joint with Parts • (1) Clamp • (1) Clip • (1) Ruler • (1) Protractor • (1) Air Muscle

Procedure 1. Borrow the clamp/mechanical joint setup from one group’s activity kit and mount it in a central location. 2. Make sure that the air muscle is securely fastened to the bike pump connection. Don’t over-tighten the

connection!!! 3. Attach the air muscle to the mechanical joint in the A position using a quick release pin. The eye bolt on

the air muscle should attach to the pin. 4. Have all the students gather around so that they can see, but make sure that they aren’t too close. 5. Inflate the air muscle by pumping the bike pump. Have the students pay attention to how much the air

muscle inflates, how much the arm moves, and how much effort it took to pump the air. 6. Repeat step 5 as needed.

Air Muscle Activity – 10 Minutes End Air Muscle Activity


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CONCLUDING DISCUSSION Q: Did the air muscle move as far as you expected it to?

• Whatever they think will be correct Q: What part(s) of the air muscle could be changed to allow it to move farther?

• Longer tube/mesh • Thicker tube

Q: Do you think an air muscle is a good replacement for a human muscle? Why or why not?

• Whatever they think will be correct. • Some possible yes reasons

o Allows for the same movements as a human muscle o Parts can be replaced if they break o Makes robotic arms more realistic

• Some possible no reasons o More bulky than human muscles o Parts can break


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MECHANICAL JOINT ACTIVITY HANDOUT Assembly 1:

ALL

Take all the parts out of the plastic container Place the team role tags upside down on the table Everyone pick a tag and read your role and description to the team

ME

Attach the clamp to the side of a desk/table To attach the mechanical arm to the clamp, take the end with the black pulley wheel and put it through the clamp from the bottom. Tighten the clamp onto the arm so that it holds it securely

See Figure 1

See Figure 2

DE

Take the quick release pin and put it through the hole in the red position (closest to joint). Lay the lanyard over the pulley

See Figure 3

Figure 1 Figure 2 Figure 3

Testing 1:

ME Hold the protractor next to the arm so that the flat side is parallel to the arm. When the TE starts to pull the arm, you will need to watch the protractor and stop the TE when the arm is at a 90° angle

TE Start to pull the string and raise the arm until the ME tells you to stop

DataE

Use the ruler to measure from the black pulley to the clip on the lanyard. Write down the length of the lanyard that was used in the appropriate box. After all the positions have been tested, rank each position from shortest to longest.

ALL Repeat the procedure for the other 3 positions


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Assembly 2:

TE Hang the weight from the hook on the end of the arm

DE Move the quick release pin back to the red position See Figure 3 Testing 2:

ALL Take turns moving the arm from its resting position (hanging vertically) to the farthest position it will move. Think about how hard it is to lift the arm and weight

DE Move the quick release pin to each of the other 3 positions (leave the weight in the same spot)

ALL

Take turns lifting the weight with the lanyard in each of the other 3 positions Discuss how hard it was to lift the arm/weight in each position Rank the positions on how easy/hard it was to lift the arm and weight assembly Write the word hard in the box for the position that was the hardest to lift, and the word easy in the box for the position that was the easiest to lift Draw an arrow from easy to hard Pick 2 positions and fill out the pros and cons of each muscle setup in the charts provided

DataE Write down the hardest and easiest lifting positions that your group decided on Conclusion:

ME Take the mechanical arm out of the clamp and remove the clamp from the desk/table Put all parts back into the container

ALL Answer the questions on the bottom of the activity handout


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Use the three types of levers drawn on the board to answer the questions. Which type of lever will require the most muscle force to lift the load? 1st Order Lever 2nd Order Lever 3rd Order Lever Which type of lever will require the least muscle force to lift the load? 1st Order Lever 2nd Order Lever 3rd Order Lever

Data Tables

Position Red Yellow Green Blue Length of Rope Used

(inches)

Shortest to Longest Easy to hard

Position: __________ Position: __________

Pros Cons Pros Cons

Follow-up Questions Which position is most like a human arm?

Which position do you think is the best for a mechanical joint? Why? HINT: Use the pros and cons from the tables from above.

What problems would exist if your bicep were actually attached at your wrist?


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MECHANICAL JOINT ACTIVITY HANDOUT ANSWERS Use the three types of levers drawn on the board to answer the questions. Which type of lever will require the most muscle force to lift the load? 1st Order Lever 2nd Order Lever 3rd Order Lever Which type of lever will require the least muscle force to lift the load? 1st Order Lever 2nd Order Lever 3rd Order Lever

Data Tables

Position Red Yellow Green Blue Length of Rope Used

(inches) ~3 ~4.5 ~6 ~7.5

Shortest to Longest Shortest Longest Easy to hard Hard Easy

Position: Red (ex) Position: Blue (ex)

Pros Cons Pros Cons

Muscle close to the upper arm

Hard to lift heavy weight

Can lift heavier weights

Muscle is attached at the wrist

Muscle doesn’t get in the way

Smaller range of motion

Forearm has better range of motion

Muscle gets in the way

… …

… …

Follow-up Questions Which position is most like a human arm?

• Red Position

Which position do you think is the best for a mechanical joint? Why? HINT: Use the pros and cons from the tables from above.

• Can be whatever they think is right • Make sure they have explained using pros vs. cons

What problems would exist if your bicep were actually attached at your wrist?

• The muscle would get in the way of your everyday life • Your arm would not be able to travel as far


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IMAGE SOURCES [1] Coude fp. 2006. Wikipedia the Free Encyclopedia. JPEG file. http://en.wikipedia.org/wiki/File:Coude_fp.PNG [2] Parekh, Alan. Tactile Robotic Hand with Air Muscles. 2007. Hacked Gadgets Forum. JPEG file. http://hackedgadgets.com/2007/07/25/tactile-robotic-hand-with-air-muscles/ [3] Air Muscle. 2012. Electrical Engineering Stack Exchange. JPEG file.

http://electronics.stackexchange.com/questions/44962/electronically-controlled-pneumatic-lift-or-something-similar

REVISIONS

Date Changes Made Changes Made By

10/1/09 Updated engineering roles, activity procedure, activity handout, and general layout/wording of lesson plan

Heather Godlewski

10/12/09 Added air muscle extension activity Heather Godlewski

01/11/2010 Spelling and grammar corrections made to lesson plan, changed on website/share folder, but didn’t re-print. Marked corrections with initials.

Konrad Ahlin

5/07/2013 Edited for grammar and syntax issues. Reorganized the format.

Todd Jackson

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Biomechanical Joint Lesson Plan - Rochester Institute of ... · PDF fileTEAK Biomechanical Joint Lesson Plan Page 2 The TEAK Project ... • Activate devices ... the output force equals