2 DOF Ball Balancer

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Vision-based Experiment for Teaching

The 2 DOF Ball Balancer module is a vision-based control experiment designed to teach intermediate to advanced control concepts. You can use it to demonstrate real-world control challenges encountered in vision-based motion platforms, such as pan-tilt cameras.

The 2 DOF Ball Balancer is based on two Rotary Servo Base Units (SRV02). Using this experiment, students can take what they learned in the one-dimensional Ball and Beam experiment, and apply it to the X-Y planar case. They learn how to:

  • model the dynamics of the ball from first-principles
  • obtain a transfer function representation of the system
  • design and implement a a proportional-derivative (PD) control system that stabilizes the ball on a plane, either at a fixed point of reference or by making it track a determined path
  • stabilize a free-moving, unrestricted ball in two dimensions
  • calibrate a camera sensor to achieve the correct ball position
  • simulate the control on a single-axis 2 DOF Ball Balancer system
  • implement the controller on the actual device and evaluate its performance

In addition to teaching vision-based control concepts, the 2 DOF Ball Balancer can be used for research in various areas, including robust control and intelligent control.

How It Works

The 2 DOF Ball Balancer module consists of a plate on which a ball can be placed and is free to move. Two Rotary Servo Base Units are connected to the sides of the plate using 2 DOF gimbals. The plate can swivel about in any direction. By controlling the position of the servo load gears, the tilt angle of the plate can be adjusted to balance the ball to a desired planar position.

The digital camera mounted overhead captures two-dimensional images of the plate and track coordinates of the ball in real time. Images are transferred quickly to the PC via a FireWire connection. Students can make the ball track various trajectories (a circle, for example), or even stabilize the ball when it is thrown onto the plate using the controller provided with the experiment.

Quanser-developed Courseware Included

The 2 DOF Ball Balancer module comes with Quanser-developed courseware. The workbook with exercises, together with quick start resources, a comprehensive User Manual, pre-designed controllers and a system model allow you to get your lab running faster, saving months of time typically required to develop lab materials.

  • Precision-crafted chassis constructed of durable ABS plastic
  • Plate mounted on a 2 DOF gimbal, which allows the plates to swivel about both axes
  • High-resolution encoders for accurate sensing and positioning of table plate in 2D plane
  • High resolution, high quality, fast frame rate CCD digital camera with FireWire connection to allow quick real-time sensing of object position in 2D plane
  • Quanser image processing software and Simulink® library provided
  • Easy-connect cables and connectors
  • Fully compatible with MATLAB®/Simulink® and LabVIEW™
  • Fully documented system models and parameters provided for MATLAB®, Simulink®, LabVIEW™ and Maple™
  • Open architecture design, allowing users to design their own controller
Calibrated base dimensions  (L x W) 41.75 cm x 41.75 cm
Table dimensions ( L x W) 27.5 cm x 27.5 cm
Camera support height 69.5 cm
Lever arm length 9.7 cm
Support arm length 14.6 cm
Camera specification IIDC 1394-based digital camera v 1.31
Camera standard resolution 640 x 480
Camera frame rate (at full resolution, Y8 format) 30 FPS
Camera pixel format Y8 in BGR format

Topics included in the Quanser-developed courseware:

Model Derivation

  • First-principles

Modeling Topics

  • First-principles derivation
  • Transfer function representation
  • Linearization

Control and Control-related Topics

  • PID
  • Multiple loops
  • Sensor analysis
The 2 DOF Ball Balancer system can be also used to teach other topics that are not included in the Quanser-developed courseware.

To set up your 2 DOF Ball Balancer workstation, you need additional components. Quanser engineers recommend:

for MATLAB®/Simulink® users for LabVIEW™ users
2x SRV02 Rotary Servo Base Unit 2x SRV02 Rotary Servo Base Unit
1x Q2-USB data acquisition device¹ 1x NI M- or X-series data acquisition device³ with 1x Quanser NI Terminal Board
1x VoltPAQ-X2 linear voltage amplifier² 1x VoltPAQ-X2 linear voltage amplifier²
QUARC real-time control software Quanser Rapid Control Prototyping toolkit Software

¹ alternatively, you can use Q8-USB, QPIDe or any equivalent NI DAQ device supported by QUARC
² alternatively, you can use two VoltPAQ-X1 amplifiers
³ NI DAQ device must be supported by Quanser RCP toolkit. Alternatively, you can use Quanser Q2-USBQ8-USB, or QPIDe


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Ball and Beam
2 DOF Inverted Pendulum/Gantry
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