Wave ball working principle

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Despite its round and simple appearance, the Wave Ball is a product of high level technology. Several sensors combined to a powerful software/hardware allow the ball to produce and increase the waves with a full control on the frequency and the amplitude.

Wave creation principle

Basis

The Wave Ball is the application result of three physical working principles :

  • Archimedes principle: wave ball is a floating sphere placed in the pool.
  • Action-reaction principle: a heavy plate (moving load) is moving up and down inside the ball shell. As the ball is placed in the water, the shell is moving up and down around the heavy plate which is not moving thanks to action-reaction principle.
  • Resonance principle: As the ball is working at one of the resonance frequency of the pool, the energy given to the pool is kept in the pool thanks to the freeboards. Each time the ball transmit its energy to the pool, the waves are becoming bigger and bigger.

Each wave is characterized thanks to several parameters such as amplitude (or height), wave length (peak to peak length) and frequency.

 

Picture 1 : Characteristics of waves
 

 

Wave Creation and control

Thanks to the upwards thrust created by the ball, a first wave is spread in the pool (figure 2). Once reflected against the wall of the pool (figure 3), the wave comes back to the ball where it will be amplified (figure 4). A computer system computes the right impulsion time in order to increase (or decrease) the waves.

 

Fig 2 : Some small waves are created by the Wave Ball
 
 

Fig 3 : The small waves are spread to the walls of the pool
 
 

Fig 4 : The waves are reflected and amplified each time they come back to the ball
 

Thanks to its electronics, the wave ball is able to compute the exact moment when the wave will be back from the wall and to predict when a pulse has to be given. The wave motion is then reinforced at each time a wave comes back to the ball. The amplitude will then grow until it reachs the one desired (fig 4).

The principle is the same as when you play on the swing and if someone is pushing you. If the person pushes you at the right moment, the amplitude of the movement will increase, even if the force with which he is pushing is weak. At the opposite, if he does not push at the right moment, if he is a little bit off the phase, the movement will stop growing and then decrease.

 

Wave Amplitude control mechanism

The more the Wave Ball transmits its energy to the water, the more the height of the wave increases. So, if we want to control the amplitude of the waves, we have to control the energy that is transferred from the Wave Ball to the water.

The transfer of energy is possible, only if the movement of the ball is shifted from the movement of the wave. The Wave Ball, to be efficient, has to anticipate its movement against the one of the wave. The shift between the Wave Ball movement and the wave movement is called the phase difference (figure 5). It is measured in degrees (°). The ball can give more or less energy by adapting the phase difference between its movement and the wave.

 

Figure 5: Wave mechanism
 

Stationary waves Amplitude control

As the waves motion is regular, the Wave Ball can determine with accuracy the amplitude of the wave and the phase difference between its own motion and the one of the wave. The Wave Ball can then adapt this phase difference in order to reduce the amplitude difference between the one measured and the one requested and thus keep the waves at a fixed amplitude.

 

Non stationary waves Amplitude control

As the waves motion is not regular, the amplitude and the phase difference vary rapidly. Thus, it is not possible to control with accuracy the amplitude of the waves. The control enables to get an average of stronger or smaller waves.

Wave Ball and electrical equipment description

The system can be divided into two fundamental units which are the floating ball in the pool and the control & electrical equipment of the ball in the technical room.

Ball composition

 

Figure 6: Wave Ball composition
 

 

  1. The moving load : The vertical movements of this load puts the ball in action. This load is moved by a rod-crank system connected to motor-reduction gear.
  2. The motor-reduction unit : Used to put the moving load in motion. The motor is an asynchronous 12V AC motor.
  3. Synchronization sensors : One principal sensor and one backup sensor, used for motor regulation purpose.
  4. Water sensor : Used for the detection of water in the ball
  5. CB50 box : Used for sensor acquisition (water and synchronization sensors) and transmission to the electrical cabinet (modulation/demodulation signal) . Contains  the accelerometer for wave frequency and amplitude control purpose.
  6. Umbilical cable : The electrical power needed is supplied by a cable coming from the electrical equipment.