Wavemaker motion system upgrades

This is a page listing potential upgrades to the wavemaker motion system. For discussion, see issue #21.

Motivation

• Wavemaker motion is noisy.
• Waves (mainly random?) are smaller than they should be.
• There is no method to disable the wavemaker from the control platform. This is not urgent, though it is a safety concern nonetheless.

Suspected causes

• Excess mechanical clearances---possibly at hinge and/or ram rod end?
  • The combination of a spherical joint and clevis attachment (relevant to issue #67)
• Less-than-smooth paddle-to-water interface (wear/rust on paddle face).
• Electrical interference with signal to servo valve.
• Software is not generating correct voltage output. Note: Voltage drop over the cable has been ruled out by examining signal at either end while generating. This may also be attributed to the lack of offset amplifier, which was removed and thrown away for some reason.
• Flow around the sides of the paddle.

Diagnostic work done

Need to add some notes from Matt and Mike here

Proposed solutions

1. Use existing motion and control system
2. Tasks * Debug software. * Check mechanical clearances. * Check for voltage drop along path from NI DAQ to wavemaker servo amplifier board.
3. Pros * Lowest cost
4. Cons * Retains a significant amount of old (noisy!) equipment, which may be unreliable. * No integration with existing emergency stop system.
5. Couple existing hydraulic power plant with newer controller, e.g., this system.
6. Tasks * Debug software. * Find EtherCAT-compatible servo control valve (these and the Bosch 4WRPDH multi-Ethernet are some options). * Send valve to ACS for qualification with the master motion controller. * Install higher resolution feedback device on hydraulic ram. * Enhance software to use existing ACS controller.
7. Pros * Lower cost and effort compared with concept 3. * Synchronization with other axes---carriage, turbine, y, and z. * Integration with emergency stop system.
8. Cons * EtherCAT servo valves are not easy to find and will take some work with vendors to get working with controller perfectly. * Retains noisy and relatively inefficient hydraulic equipment. * May require new hydraulic cylinder, if newer feedback device cannot be installed.
9. Upgrade to electric linear actuator coupled to newer controller ⭐
10. Tasks * Debug software. This should only take a few days. * Verify paddle dynamics calculations. * Size, purchase, and install electric linear actuator, replacing hydraulic ram. Minarik already gave us a quote based on the calculations above. Possible manufacturers include Precision Technology and Exlar. Will be approximately $15k in hardware. Installation could take a week depending on how much modification has to be done to the existing ram mounts. * Remove hydraulic power plant, replacing with servo drive in additional electronics cabinet, spliced into existing EtherCAT control network. AC wiring from the 2012 DOE grant upgrades cost around $5k, so this should be a little less. This will take about a week or two. * Enhance software to use existing ACS controller. This will actually be quite simple, and only take a few days.
11. Pros * Energy savings by eliminating pumping against bypass valve when not making waves. * Quietest option. * If we used a Kollmorgen AKD drive or similar, electronics would be essentially "plug-and-play." * Synchronization with other axes---carriage, turbine, y, and z. * Integration with emergency stop system.
12. Cons * Highest cost and effort to implement.

Summary and comparison

Concept	Cost	Effort	Safety	Accuracy	Efficiency	Reliability
1	low (~$500)	low	no change	no change	no change	no change
2	moderate (~$5000+)	moderate	improved	improved	no change	improved
3	high (~$20000)	high	improved	most improvement	improved	most improvement