11/5/2018: Preliminary Design Review
Updated dimensions: 48” x 24” x 78”
We have modified our design concept to include a modified Concept2 rowing ergometer, rather than a self-manufactured rowing machine. The C2 is equipped with embedded force data collection in the Performance Monitor (PM). A schematic of our new expected experimental design is shown below:
We intend to remove the track and seat of the C2 machine to accommodate a vertical rowing motion in microgravity. A support frame of 80/20 stock will also include a pulley that redirects the chain upward. Force data will also be collected from sensors placed on the foot plate. We are currently testing commercially available insole force sensors, as well as a traditional load cell. An overview of the data collection system is shown below:
Our team conducted a first trial of this setup using a traditional (unmodified) C2 rowing machine. This is shown in the video below. Both the IMUs and the tracking markers can be seen on the subject as he rows. The wires running from the footplate are connected to the insole force sensors, taped down for security. The initial force data from this experiment was very noisy. We will continue to refine the data collection and filtering process.
10/9/2018: Electrical Schematic update
Our only electrical system will be a simple circuit connecting 4 load cells to a battery and microcontroller for recording information. A load cell amplifier is necessary to condition the signal. A rough draft of this system look as follows.
10/6/2018 System Concept Artwork
Below shows some concept rendered CAD work for the project. The system consists of a fairly standard rowing ergometer mounted to an aluminum plate. This aluminum plate is fastened to 4 load cells, which are then fastened to another aluminum plate which is mounted to the floor of the aircraft. So, there are 4 load cells sandwiched between two aluminum plates. This will measure the total force in the direction normal to the aluminum plates.
In order to maintain bone density and muscle mass, loading of the musculoskeletal system is necessary. While some exercise more than others, the constant weight of the human body due to gravity can maintain sufficient musculosketetal health. In microgravity, the removal of constant loading on the skeleton leads to loss of bone density and muscle mass. In order to counteract this, humans living in microgravity must exercise extensively. Exercise devices exist on the International Space Station (ISS), including a treadmill, cycle ergometer, and resistive squat-type machine, but these devices are generally consume a large volume of space in the ISS. For a long duration flight to Mars, space is far more limited—to a relatively small crewed capsule. This necessitates the design of more compact exercise device. Rowing ergometers offer the benefit of a diverse resistive and cardiovascular exercise in a compact space.
But how can one evaluate if an exercise is sufficiently loading the musculoskeletal system? Generally speaking, the analysis of inverse dynamics of the human in an exercise environment does this. Given positions of the human skeleton and known loads on the human body, an optimization problem can be solved to compute the forces and torques on individual muscles, bones, and joints. Measuring the loads on the body is generally tractable—an exercise device can be outfitted with a force plate or a power meter. However, measuring the human skeletal pose is less simple—typically performed through optical motion capture (OCM). This process typically involves placing markers on the human body and then using a large set of cameras to estimate the marker positions—then doing a separate modeling and optimization problem to understand the relationship between these markers and the human skeleton. This process is expensive, cumbersome, but more importantly, intractable in space. The cameras require constant recalibration and can be destroyed by radiation. A feasible alternative may be wearable inertial measurement units (IMUs), small inexpensive sensors which can estimate orientation when warn on the human body.
This project seeks to address two primary research questions:
1) Are IMUs a feasible solution to estimate human skeletal pose in microgravity for use in an inverse dynamics pipeline?
2) Is rowing and an associated compact ergometer a practical and sufficient exercise to maintain bone and muscle mass?
NOTE: Gonna keep this private for few weeks or so until it’s in a presentable public state with info
work with third parties to see what sensors they want to include
Submit COUHES paperwork by October 25
hash out experimental protocol
upload initial concepts of hardware (we’ll do the mechanical analysis later)
upload info on sensors/what they measure
discuss how these previous two combine to give inverse kinematics