Vision tracking in QUARC using OptiTrack

Measuring the position of an object is fundamental for control systems development. For certain applications, for example unmanned aerial vehicles or ground vehicles, this can be quite challenging. That is why we have integrated the NaturalPoint OptiTrack camera system into QuaRC. The OptiTrack camera system consists of three or more synchronized infrared (IR) cameras that capture images containing reflective markers within a workspace. The cameras emit IR light from an array of IR LEDs, and the IR light reflected by the special markers is picked up by the cameras and seen as bright spots on the image. Software then processes the images from the collection of cameras and determines the position of each marker in the 3D workspace. Rigid bodies (rigid shapes made up of 3 or more reflective markers) can be constructed and tracked in 6-DOF (position and orientation).

We have integrated the OptiTrack camera system in QUARC so that the designer can use a simple set of QUARC blocks in Simulink to track individual markers or rigid bodies. To test the performance of the system, we wanted to see if it was possible to control a standard inverted pendulum experiment using visual feedback instead of the standard encoder feedback. To control the inverted pendulum you must be able to measure the pendulum base arm angle and the angle of pendulum. We placed refective markers on an inverted pendulum experiment and used a simple QUARC block to interface with the OptiTrack system to measure the marker positions. Knowing the marker positions, we can determine the angle of the pendulum base arm and the angle of the pendulum so that it can be controlled.

The following video shows the results of this experiment. As you can see, it is possible to stabilize the inverted pendulum using vision-based feedback. The OptiTrack system combined with QUARC is a powerful new control tool, opening up the possibility for many new control experiments. Objects that were previously difficult to track, such as indoor autonomous vehicles, can now be tracked by adding reflective markers.

Engineering Education - How we can help

Here are few ideas from Sunny Ray, Quanser's Academic Solutions Adviser on how teaching and research universities can gain a competitive edge.

3 DOF Gyroscope

Gyroscopes have become of great practical interest as they are widely used in control and guidance systems for air, sea and space vehicles. Some examples include air plane automatic pilot, rocket vehicle launch guidance systems, space vehicle attitude control and submarine inertial autonavigator systems. All of these applications make use of the special dynamic properties offered by gyroscopes. As the industries involved in the above mentioned applications are always growing, the demand for availability of up to standard research tools also rises to ensure desired studies can be carried.

Quanser is soon releasing a new such product called the 3 DOF Gyroscope, depicted on the left. The device consists of a rotating disk mounted inside an inner gimbal which is in turn mounted inside a second outer gimbal. This whole structure is supported by a rectangular frame that is free to rotate about its vertical axis of symmetry. This scheme results in three degrees of freedom for the gyroscope disk. The structure is masterfully engineered to provide minimal friction on rotation axes. This makes the 3 DOF Gyroscope a great choice for research in spatial applications of gyroscopes as the zero friction of space is almost nearly achieved by the device! Each axis as well as the disk itself is actuated using a separate motor while digital position measurement on each of these axes is done via high resolution encoders. While both gimbals and the outer frame are free to rotate about their rotation axes, the frame and outer gimbal are designed such that they can be also be fixed on desire. Therefore a whole variety of experiments can be performed.

The 3 DOF Gyroscope also comes with an extensive curriculum that uses MATLAB and Quanser's QuaRC software to cover a variety of experimental tasks using the gyroscope plant such as stability analysis, root locus design, non-minimum phase effects, LQR state-feedback control and friction compensation schemes. In the video below, the plant is simulated using the Virtual Reality toolbox and QuaRC to perform position control on the gyroscope angle about the vertical axis. The yellow plot shows the reference applied in degrees while the purple plot is showing the output. Notice that as a direct result of the gyroscopic effect, the horizontal axis is actuated to control the angle about the vertical axis. That's the magic of gyroscopes!

(Note: 3 DOF Gyroscope is scheduled for release in March 2009)

Shake Table I - 40 - A New Addition to Quanser Shake Table Collection

The sleek, compact, and powerful Shake Table I – 40 is a new addition to the Quanser line of seismic devices. The system is 7.6 cm high, 57.5 cm long, 12.7 cm wide, and weighs 5.9 kg – thus it can be used as a portable, tabletop shaker solution. Although compact, this table is able to accelerate a load that weighs 1.5 kg up to 1.0 g. The top stage is mounted on a high-quality, low backlash linear guide with a total travel of 40.0 mm (i.e. ± 20.0 mm) and is driven using a high torque direct drive motor. When operating, the stage movement is extremely quiet.

This can also be used with the One-Floor Active Mass Damper in order to perform structural engineering analysis or develop a controller that reduces the deflections of the building while, for instance, the table is running an earthquake.

The Shake Table I -40 can be run on a PC with the QuaRC control software. This can be done either through Matlab/Simulink or using the STI-40 Software shown below. The STI-40 Software enables users to quickly get started and command signals such as sine wave, chirp, and sample earthquakes all through an easy-to-use GUI. Only QuaRC and the LabVIEW Run-Time Engine, which is free to download, are needed to run this program (no need for Matlab/Simulink). This software can even be published to a website for users to log on and control the table remotely.

- Mitch -

(Note: Shake Table I - 40 is scheduled for release in March 2009)

QUARC: Channel Selection Dialogs

Some of the highly anticipated new features of our upcoming 1.2 version of QuaRC are the added Channel Selection and Channel Selection From Image Dialogs.

The Channel Selection Dialog is a generic user interface window to choose a list of channels from the set of I/O channels available for the data acquisition card being used. As an example, the screen capture below depicts a QUARC Channel Selection Dialog employed to select a set of some of the digital inputs available for the Quanser Q8 board. More specifically, the list on the left shows the available I/O channels from which the user may choose. The list on the right shows the channels that have already been selected:

Digital Input Selection using the Channel Selection Dialog

The Channel Selection Dialog is available for all of the data acquisition cards supported by QuaRC (totalling 46 in QuaRC 1.2!) and is typically accessed from either a HIL Initialize block or any other QuaRC HIL block used in I/O interfacing.

In addition, the Channel Selection Dialog works in concert with the Channel Selection From Image Dialog, which represents an interactive picture of the currently selected data acquisition card's external connector or terminal board. The Channel Selection From Image Dialog is a generic interface allowing the user to precisely mouse select a set of I/O channels directly from a picture of the HIL card's external connectors as well as visualize the locations of the I/O pins and/or connectors previously selected from the standard Channel Selection Dialog. This is illustrated in the screen capture below where the digital inputs from our previous selection are located and marked on the Q8 terminal board:

Digital Input Selection using the Channel Selection From Image Dialog

Sometimes the connection pins can be quite small and it becomes necessary to magnify the image to be able to see all the different channels/pins. This is why zooming in and out of a desired area of the image can be easily performed with the Channel Selection From Image Dialog so that I/O channels can be accurately identified and selected. As an illustration, the screen capture below shows in detail the previously selected Q8 digital inputs on the magnified Q8 terminal board digital header:

Board Magnification using the Channel Selection From Image Dialog

Last but not least, the Channel Selection Dialog also identifies and shows potential conflicts between selected and selectable channels. The screen capture below provides an example where the Q8 bidirectional digital lines which were previously selected as digital inputs are marked as potential conflicts if they were to be also selected as digital outputs:

Digital Output Selection showing Potential I/O Conflicts

India Roadshow

Dear All,

I recently had the good fortune of visiting India, a country beaming with youngsters who are on the cusp re-writing history. From the minute the airplane door swung open, I knew I was in for quite the experience. Over the two weeks I spent immersed in this colorful and vibrant culture, I was pleasantly taken aback by the array of mouth watering dishes and their assortment of appetizers and sweets.

The good people at Cybermotion, Quanser’s Indian distribution team, showered me with their warm hospitality and inspired me with their drive and dedication towards impacting the academic and industrial world of controls and automation. Anand and Praveen, two brothers spear-heading this ambitious team of more than 60 highly energetic and hard-working individuals, are visionaries in many respects. On several occasions, I couldn’t help but comment on the similarities between Quanser and Cybermotion.

During the week, we spent a great deal of time presenting to and working with professors from some of the top Universities in India such as IIT. The decisions made and the courses cultivated at these top institutions has an incredible impact on potentially hundreds of institutions around the country. It gave me a great sense of pride to present on behalf of Quanser and to see that our control solutions are found in labs all over the world!

Cheers,
Sunny

Team building - James Bond Style

SRV-02, QDB8 and Wrenchturn, as well as over 30 other Quanser secret agents gathered on January 28 at a secret location with a code name Laser Quest (that's why you got voice mail on Wednesday). Even a raging snowstorm didn't stop the devoted agents (every time Quanser organizes an event, a bad weather hits. We will keep you posted on when to expect next snow storm or tornado).

The goal of the secret mission? Kick off a New Year with a Champaign toast to Quanser's 20th Anniversary and celebrate our hard work. Of course, secret agents live for action - just look at the number of new solutions Quanser agents bring out every year - but this time it was about the agents themselves, not the gadgets they love to create. Agents were assigned to teams where they set targets and worked out strategies to protect the team 's base, collect "bugs" and eliminate as many "enemy" agents as possible.

It was no surprise that both teams worked together pretty well - after all, we work together in a real life - and have a lot of fun! What did come as a surprise were the sharp-shooting skills of White shark (a.k.a. Derek Wight) who won the first game and ninja-like Sashimi (a.k.a. Luke Cho), a celebrated "bug collector" for the team Q.

Just as everyone was running out of ammunition - Zofo's (a.k.a. Paul Gilbert) presentation brought everyone to life. Zofo entered the room in true Bond style with the 007 theme song and a glass of Martini (shaken, not stirred). He outlined for the rest of the agents the goals and strategy of the whole Quanser team for this year. Agent Tut (a.k.a. Jacob Apkarian) who founded the company 20 years ago, added few words to highlight the success of the now adult Quanser. And of course, there was a cake (expertly cut by agent Tut) and cigars.

By the way, aren't you curious which team has won? Oh, it doesn't matter - we are all one team.