Design team members: Roanne Sones and Allan Colquhoun

Supervisor: Prof. Erik Kubica

Background

Volleyball is an appealing and challenging game. Although growing in popularity and improving in quality, it is very difficult to refine your skills without many players participating. For many elite athletes and teams, this is a concern.

Blocking in volleyball involves between one and three players of the opposing team jumping in unison to create a wall above the net with their hands.  Ideally this wall will block the ball down to the court on the attackers side. An effective block is often the difference in a game, and successfully avoiding the block is a skill all players seek to improve.

Creating a mechanical blocking system for our fourth year project will allow players to develop the essential skill of spiking the ball around the block, without requiring the presence of other elite players to form the block.  In team practice situations, players won’t be required to perform the blocking, allowing all players to practice their spiking skills at the same time, if so desired.

Having both spent significant amounts of time playing varsity volleyball, the problems noted above have been very apparent and often frustrating for us on a personal level. Given the chance to combine two activities (engineering and volleyball) to which we have dedicated so much of our time over the last five years and provide an improved training environment provided the motivation for this project.

The first step in this project is to determine the requirements to build a volleyball blocking system prototype that will improve the training for an advanced volleyball player. Having established these requirements, designs will be considered that will attempt to address them. The various potential designs will be evaluated against the requirements and a final design will be selected. The final stage of this project will be to completely design the selected design and attempt to build a fully functional prototype.

Project description

At this point in time, we are working on fully designing our selected, final prototype design. The following describes some of the major components of the system, the alternatives considered for each, and a description of the final design.

One of the first steps we took to begin considering possible designs was to establish major components of the system. The major components consisted of: the blocking surface, the control system, the mechanical system and the anchoring system.

Blocking Surface
The blocking surface is the component of the system that will be above the net and will ‘block’ the ball attacked by the spiker. It was important to develop a blocking surface that reflects the ball realistically, that won’t be broken, and was light enough to dynamically move. Eliminating heavy materials such as wood and metal, we were left with lexan and acrylic. Performing stress analysis and investigating the reflection properties of lexan and acrylic, it was determined that the blocking surface would be made of lexan.

Control System
The control system provides the system the intelligence it needs to accomplish the dynamic aspects of its requirements. Responding to inputs and triggering outputs were to be handled by a PC, a micro controller, a PLC or simply a series of switches. At this point, a final control system hasn’t been selected. However, a PC is unlikely due to cost and difficulty of I/O, and a series of switches is unlikely due to the limited control offered.

Mechanical system
The portion of the system involved in moving was dubbed the mechanical system. There were two main options that were considered for the mechanical system. The first consisted of pneumatic cylinders being attached to the blocking surface. When the compressed air source provided pressurized air to the cylinder, the blocking surface would be raised into blocking position. There could be up to three cylinders, each controlling one blocking surface. The other option was to use a pulley system using motors. Stepper motors, AC, DC and Universal motors are all options for a motor-based solution. Due to cost, pneumatic cylinders have been eliminated. The type of motor has not yet been established, as cost/benefit analysis for the various types is ongoing.

Anchoring System
The final major component was the anchoring system. This provided the means by which the system would remain stationary during the impact of the spike. Two approaches were considered, attaching the anchoring system to the pole system, and having a freestanding anchoring system. Market research revealed that one type of pole dominated the market, with one other type having some market share. However, the ease installation and removal, the flexibility and the safety concerns led us to select a freestanding anchoring system.

Selected design

Although we arrived at our final design through the methodology described below, the discussion of the major system components provides good insight into the final, selected design. The final design is a motor-based design that will be anchored via a freestanding base. This base will house both the motors and the control system, when selected. The blocking surface will be raised into place by a pulley system and the structure will be clipped to the net at the top of the net to ensure the system will be able to withstand the force of a volleyball spike. A simple diagram of the system can be seen below in Figure 1.


simplified diagram of selected prototypesFigure 1: Simplified diagram of selected prototype

Design Methodology

After numerous brainstorming sessions, the group finally settled on seven distinct prototype designs. The immediate goal at this stage of the design process was to determine what prototype should be selected for development.

In order to select only one prototype for development, we needed to come up with a set of criteria to evaluate the prototypes. The criteria selected were representative of high-level design requirements and were used to easily differentiate between the different prototypes. Table 1 details the selection criteria and the average metric in the unit of measurement of the criteria as determined by the group.

Selection Criteria Average Metric
Cost Less then $300
Ease of manufacture Can be completed in 4 months
Ability to reflect the volleyball Will accurately reflect the volleyball
Ability to simulate double block Can create a single, double, cross and line block
Power requirements of system Will require only an AC source to run
Ease of replacement components Cost and location of replacement products
Portability Can be carried by one person

Table 1: Selection and average metric used as reference for different prototypes

With our selection criteria determined we then chose to set up a concept-screening matrix. Each prototype was deemed above average, average or below average for selection criteria in Table 1. This ultimately eliminated two prototypes that were below average on almost all aspects of the selection criteria.

The field was now narrowed down to only five prototypes. To select the final prototype for development a concept-scoring matrix was created. This primary purpose of this matrix was to take the priority levels of the selection criteria into account. The different priority levels were given associated weights that were used to consider the overall ranking of each prototype. Due to the nature of the project, the group decided to place a weight of 25% to both cost and ease of manufacture. As the project is only 8 months in duration, and we are still paying tuition, these are the limiting factors to our success.

Although a fairly close result, in the end Prototype 7 proved to most favourably meet the selection criteria.