T.E.A.K. - BioengineeringBiomechanical JointPage 1
TEAK
BIOENGINEERING
Biomedical Engineering Kit
Biomechanics of a Joint Activity
Instructor Preparation Guide: Biomechanics of a Joint
Bioengineering Overview
Bioengineering is the use of engineering principles to tackle challenges in the fields of biology and medicine. Bioengineering applies engineering designprinciples 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 things. Areas of biomechanics that will be covered in this lesson include prosthesis, robotics, and materials. Prostheses helppeople with disabilities perform tasks that they could not do naturally. Advances in robotics are 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 a Human ElbowFigure 2 – Robotic Hand with Air Muscles
Mechanical Advantage
T.E.A.K. - BioengineeringBiomechanical JointPage 1
Mechanical advantage is a factor in 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 as 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 what would be 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 therefore 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.
Resources
Image Resources
- Figure 2:
Date: February 3rd, 2009Time: 1:00 PM
- Figure 1:
Date: February 3rd, 2009Time: 12:00 PM
Activity Preparation Guide -Biomechanical Joint
Overview
This kit contains discussions and an activityto 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 to work through these issues to construct and test a simple biomechanical elbow joint.
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 in order to determine the best design
• Describe what an air muscle is and how it works
Engineering Connection
Engineers work with doctors to create solutions to problems that arise within surgical and medical environments. Due to advancements in surgical operations and in the field of robotics in general, the need for robotic devices that can mimic human joint motion has been increasing over the years. By studying human joint motion, engineers are able to optimize the range of motion a typical person possesses and then apply that range of motion through a mechanical system to carry out a function with great precision and accuracy.
Activity Description
Biomechanics of a Joint Activity: 30 Minutes
During this activity, the students will work in teams to figure out the best way to move a biomechanical elbow. They willlearn about mechanical advantage, and then use what they learned by trying different attachment positions for the muscle. After they have tested all of the potential solutions and analyzed the data, they will make their decision as to which system design creates the best solution.
Student Engineering Team Roles
Mechanical Engineer – Responsible for setting up the mechanical joint
Design Engineer – Responsible for modifying the design features
Test Engineer – Responsible for making the mechanical joint move
Data Engineer–Responsible for collecting and recording data
Extension Activity:
Air Muscle Activity:10 Minutes
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.
New York State Learning Standards
New York State Health Learning Standards
a.) Standard 3: Resource Management
- Students: Distinguish between invalid and valid health information, products, and services.
- Students: Analyze how the media and technology influence the selection of health information, products, and services.
New York State Technology Learning Standards
a.) Standard 1: Engineering Design
-Students will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to pose questions, seek answers and develop solutions.
- Students:
· Activate devices
· Recognize why an object or choice is not working properly
· Recognize how a defective simple object or device might be fixed
· Under supervision, manipulate components of a simple, malfunctioning device to improve its performance
· Design a structure or environment (e.g., a neighborhood) using modeling materials such as LEGO Duplo blocks, model vehicles, model structures, etc.)
b.) Standard 5: Technological Systems
- Students will apply technological knowledge and skills to design, construct, use, and evaluate products and systems to satisfy human and environmental needs.
- Students:
· Identify and operate familiar systems
· Assemble simple systems
New York State Science Learning Standards
a.) Intermediate Standard 1: Analysis, Inquiry, and Design.
- T1.1: Identify needs and opportunities for technical solutions to from an investigation of situations of general or social interest.
- T1.1a: Identify a scientific or human need that is subject to a technological solution which applies scientific principles.
- T1.3a: Identify alternative solutions base on the constraints of the design.
b.) Intermediate Standard 6: Interconnectedness
- 1.4: Describe how the output of one part of a system can become the input to other parts.
- 4.1: Describe how feedback mechanisms are use in both designed and natural systems to keep changes within desired limits.
- 6.1: Determine the criteria and constraints and make trade-offs to determine the best decision.
Resources
1.)
2.)
3.)
Note: Many of these resources were used in assisting the creation of the following Lesson Plan and we want to thank and reference them for their valuable instruction.
Biomechanics of a Joint
Duration
50-55 Minutes
Concepts covered:
Bioengineering
Biomechanics
Mechanical Advantage
Medical Applications
Bioengineering Discussion:5 Minutes
Background Information:
Bioengineering is the application of engineering principles to address challenges in the fields of biology and medicine. Bioengineering is the application of the principles of engineering design to the full spectrum of living systems.
Group Discussion: Bioengineering Background
(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)
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.
What do you think engineering is? What do you think it means to be an engineer?
- A technical profession that applies skills in:
- Math
- Science
- Technology
- Materials
- Anatomy
- 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:
- Prosthetic Joints
- Artificial Limbs
- Hearing Aids
- Artificial Organs – Heart, Lungs, Etc.
- Dialysis Machines.
- Contact Lenses.
Biomechanics of a Joint Activity Introduction: 10 Minutes
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 Definitions:
- Mechanical Advantage – A factor by which a mechanism multiplies 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
Group Discussion: Mechanical Elbow
(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)
Can you think of an example of a lever?
(There may be more correct answers than the ones listed.)
- See saw
- Wheel barrow
- Wrench
- Bicycle Hand Brake
- Your arm!
Do you think these levers make it harder or easier to do work?
- Easier, because of mechanical advantage.
Discuss the 3 orders of levers and draw diagrams on the board.
- First Order Lever
- The fulcrum is between the effort and the load. Mechanical advantage = 1
- EX: See saw, scissors
- Second Order Lever
- The load is between the fulcrum and the effort. MA is greater than 1
- EX: Wheelbarrow
- Third Order Lever
- The effort is between the fulcrum and the load. MA is less than 1
- EX: Shovel, your arm!
If someone needed a mechanical limb (such as an arm), what kind of simple machine should they use?
- A lever
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.
What do engineers need to know to create a mechanical body part?
(There may be more correct answers than the ones listed.)
- 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(per group)
-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.
Procedure
- Have the students get into 5 groups.
- 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!!)
- Hand out one activity worksheet to each group.
- Instruct students to discuss the first three questions with their group and come up with answers.
- 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.
- 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.
ALLTake the all ALL 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.
MEAttach 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.
DETake 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.
TEMake 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.
METake 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.
TEStart to pull the string and raise the arm until the ME tells you to stop.
DataEUse 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.
ALLRepeat the procedure for the other 3 positions.
TETake out the hanging weight. Hang it from the hook on the end of the arm.
DEMove the quick release pinback to position A.
ALLTake 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.
DEMove thequick release pin to each of the other 3 positions. (Leave the weight in the same spot.)
ALLTake 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.
DataEWrite down the hardest and easiest lifting positions that your group decided on.
METake the mechanical arm out of the clamp and remove the clamp from the desk/table. Put all parts back into the container.
ALLAnswer 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.