Ottobock’s Myo Plus is a myoelectric pattern recognition system that is compatible with Ottobock’s MyoBock family of terminal devices. These include the bebionic hand, System Electric Greifer, and Myoelectric Speed hands.
A Quick Look at Myo Plus
The following video provides a quick overview of the Myo Plus pattern recognition system:
Before reading further, a little background information may be helpful. To obtain this, please see our master article Myoelectric Pattern Recognition for Bionic Arms & Hands, which includes a basic description of how pattern recognition systems work.
As that article indicates, there are a few key areas crucial to the success of any myoelectric pattern recognition system. These are:
- basic technology;
- evaluation support;
- setup & calibration;
- recalibration by the end-user.
We will examine Myo Plus in each of these areas.
There is a spectrum of pattern recognition technologies:
A simple system may use some form of pattern recognition or artificial intelligence to clean up myoelectric signals but it still relies on the user to explicitly contract certain muscles to control a bionic device. This is not a true pattern recognition system. True pattern recognition systems allow the user to attempt to move a bionic device in the desired manner, which then triggers a pattern of muscle movements. It is this pattern that is translated into bionic device commands, not the movement of specific muscles.
Universal systems offer true pattern recognition. They are called “universal” because they are capable of interfacing with many different types of bionic components, including elbow and wrist components.
Myo Plus is not a true universal system because it only works with Ottobock’s MyoBock family of terminal devices, which does not include an elbow component. But it does otherwise behave like a universal system for this particular set of devices.
How does Myo Plus function? Let’s walk you through the typical chronology of its evaluation, configuration, and subsequent use.
The first step for a prospective user is to evaluate whether he can benefit from Myo Plus.
A proper evaluation starts with a physical examination of the user’s residual limb by a prosthetist trained in the setup, calibration, and use of Myo Plus compatible devices.
The prosthetist will then attach a diagnostic cuff called Myo Cuff to the residual limb:
The cuff collects data from the sensors and transmits it via Bluetooth to a Myo Plus software application. This app allows the prosthetist to test the ability of the user to generate clear and repeatable patterns of muscle movement.
The prosthetist can also use the evaluation process to help select the appropriate terminal device, as well as to determine the design of the physical socket and the number and placement of the required sensors in that socket.
Setup & Calibration
The Myo Plus app is used to calibrate a Myo Plus solution.
Calibration is the process of mapping patterns of muscle movements to the actions of a bionic device.
A pattern of muscle movements can look as follows in the Myo Plus app, where each numbered node represents data from a corresponding myoelectric sensor:
This pattern can then be assigned to a specific hand movement:
Because muscle patterns can change when the arm is in a different position, recordings for the same movement are made in three different arm positions (arm extended, arm hanging down, arm bent at the elbow).
These the main elements of the system. As the saying goes, the devil is in the details, and the details here are:
- ensuring that the pattern for each movement is distinct from the patterns of all the other movements;
- training the user to be consistent in those movements.
The Myo Plus app can also be used for user training/practice. As displayed in the previous image, the app can rate the quality of each movement from one to five stars.
Users can practice each movement until they are consistently capable of generating high-quality pattern signals.
This type of training is not as sophisticated as the training provided by Infinite Biomedical Technologies for its Sense pattern recognition system, which uses interactive games to encourage users to practice. But it should be sufficient to allow a dedicated user to achieve success.
One of the challenges of myoelectric control systems, especially those dependent on skin-surface sensors, is that the state of a user’s residual limb is not constant. It can change with things like temperature (swells when hot, shrinks when cold), humidity (skin sweat), and muscle fatigue.
When this happens, users need the ability to quickly recalibrate their pattern recognition system. The Myo Plus app allows users to do this. The process is not quite as convenient as the push-button feature provided by Coapt Engineering’s Gen2 system but, again, it should be sufficient for users to adjust their calibration as needed.
User Feedback Survey & Results
Are you or have you previously been a Myo Plus user? If so, please share your insights with others looking at Myo plus as a possible pattern recognition system.
We do not yet have a sufficient number of survey participants to publish fair and accurate results for the Myo Plus system.
As soon as we do, we’ll update this section.
Considerations Before Buying Ottobock’s Myo Plus System
Without sufficient feedback from independent users, we’re not yet able to form a complete opinion about Myo Plus.
However, the system does seem to have checked all the boxes when it comes to delivering a complete myoelectric pattern recognition system. And if you’re intending to purchase one of the Myobock family of bionic devices, the Myo Plus system should probably move to the top of your list.
The real question for prospective users is whether to opt for a proven pattern recognition system like Myo Plus now or to wait until new devices from Atom Limbs, BrainRobotics, and Esper Bionics come to market with promises of even more advanced pattern recognition systems.
As it stands now, it will likely be 2022 before those new devices are available and another year or two after that before we get sufficient user feedback to know if they have delivered on their promises.
In other words, a lot of this will come down to each prospective user’s purchase window and risk tolerance.
If you are considering a dual-site, direct-control myoelectric system, do not miss our article on Finding the Right Myoelectric Control System.
For a comprehensive description of all current upper-limb technologies, devices, and research, see A Complete Guide to Bionic Arms & Hands.
Click here for more information on Ottobock.