1.1 Hardware Facts
2.1 3D/2D Polar Plot
2.2 Digital Chart
2.3 Video Player
2.4 Time Series Plot
2.5 Maneuver Estimation
2.7 Sail Shape Analysis
2.8 Wind Shifts
2.9 Classical Instruments
Within the PerforManD system every boat is equipped with a wind anemometer to measure apparent wind and a paddlewheel or impeller velocimeter to measure speed through water. Further sensors include video camera(s), GPS position, orientation and speed and an inertial measurement unit. When possible, instruments have been housed into the data aggregation unit which, beside its data logging capabilities also includes telemetry modules like Wi-Fi and Bluetooth for wireless communication. Since the use case of PerforManD aims at small boats and dinghies, great care has been taken that all sensors can be mounted to the sail boat without permanent destruction like e.g. drilling holes. Furthermore, no cabling is required since all sensors connect wirelessly to the data aggregation unit or are embedded in it. This allows for fast setup of the system on an individual boat. Compared to big boats instruments all components have been miniaturized with respect to size and weight. Both, the data aggregation unit and the sensor nodes are powered autonomously by lithium batteries in addition to solar panels which allow for data logging sessions of approximately 8 hours.
To provide the coach with access to real-time data during training sessions, a Wi-Fi module with external antenna is mounted onboard the coach boat to extend the connection range of the visualizing and analyzing unit. . If several boats are in range, the coach is able to switch between the individual boats or to monitor the data of multiple boats simultaneously. This allows for either the direct performance comparison of boats sailing in similar conditions, the monitoring of a complete fleet, or giving special attention to a particular boat by dedicated exclusive monitoring.
- Course over Ground (GPS)
- Speed over Ground (GPS)
- Heading (mag. Course)
- Boat Speed (water log)
- Apparent wind angle (wind sensor)
- Apparent wind speed (wind sensor)
Audio / Video recording
- Crew Observation (camcorder)
- Sail Shape recording (camera)<(li>
Inertial Measurement Unit (IMU)
- Transversal Acceleration (3 components)
- Ratations (3 components)
- Rudder angle
- Local stresses and tensions
- Mast top twist / distortion
Data Logging (microSD card)
- 8 Gbyte per day (99% audio/video)
The client software and its visualization and analyzing tools are aimed to give a coach or performance analyst the possibility to visualize data measured using the PerforManD sensor system and to assist the assessment in sailing performance with additional analysis tools. In addition a review mode is available for visualization and analyzing of the recorded measurement stream during debriefing sessions of sailors and coaches.
A velocity polar diagram showing the speed a sailing yacht can achieve depending on true wind speed and direction is widely used by yacht designers. It allows assessing a particular design and comparing it to others. Velocity polars are also valuable to the sailor. They provide operational parameters like tack and gybe angles and cross overs for different sail sets. However primarily they provide the maximum speed of the yacht as a target, depending on wind conditions. A velocity plot provides a target for the sailor to achieve during training sessions. If he routinely exceeds the target, the velocity polar is invalid and has to be modified. Obviously an accurate velocity polar is of great value to a coach of a dinghy.
Standard velocity polar diagrams are based on an aerodynamic and a hydrodynamic model of the sail boat derived from experimental or numerical flow analysis. The PerforManD system uses a different approach: it generates a velocity polar from performance measurements aboard. These measurements are obtained while sailing and do not need any special attention. To this end PerforManD uses a three dimensional description of the boat speed depending on TWA and TWS, where TWS is given as a continuous value rather than a set of discrete values as a conventional polar plot. The geometric representation of this three-dimensional boat performance description is a torus surface in a three dimensional cylindrical coordinate system.
A conventional polar plot can be derived easily from this 3D-torus. Any horizontal intersection through the torus at a particular height, e.g. wind speed, gives the velocity polar for this particular wind speed. PerforManD presents the intersection of the polar torus at the currently measured wind speed. In addition the current boat speed at current TWA is also shown in the diagram, see Figure 3. A conventional 2D polar diagram derived from the torus is shown in
Performance relevant data such as wind and boat speed and angles, respectively, are acquired with a data rate of 5 to 10 Hz and averaged to 1 to 2 Hz. A filtering procedure excludes maneuver situations and handles wind gaps or shifts. Manoeuvers are detected using the AWA and other course-relevant values.
While the process of obtaining measurement data streams for polar torus generation is fully automated, it is assumed that many hours of sailing are necessary to achieve a plausible velocity polar torus. At the beginning of the use of a PerforManD system the torus will be incomplete and inaccurate while over time the entire wind range will be covered and accuracy will grow. It is possible to import existing diagrams which will be fitted by additional measurements. The imported diagrams could be either diagrams generated by the PerforManD-Software or by an external VPP.
A digital chart is available within PerforManD, showing any dinghy registered and involved in the training process. In online mode this can serve as a conventional navigation aid. In addition to position it provides information of the current sailing state (speed, wind, etc.) of any boat linked to the coach boat.
In review mode the digital chart can show any boat, which has been equipped with the PerforManD system and thus provides recorded data streams. Consequently a debriefing session can visualize an entire fleet simultaneously. For each boat the local wind and performance measures are available. This is of some help for debriefing sessions not only for the orientation of the sailors; but also it can provide information of the relative performance of the boats, how they behave tactically and how they take advantage of the local wind.
With the video player, it is possible to get to know the situation of the boat and the sailors. With a camera position chosen appropriately one can get information like the trim, the wave conditions and the behavior of the sailors. In review mode, the video player is available as well, showing recorded media streams. The video is synchronized to all other instruments and with other boats. This allows correlating action on board with respective performance data. The video mode will be available for the next prototype release of the PerforManD system.
Time series plot allows showing any available data stream over time, whether it is a native, directly measured stream or a derived one. Its purpose is manifold: it can be used to visualize the change of wind data over time or the correlation between boat speed and motion, for example in waves. It is used to detect wind changes, manoeuvers or performance changes due to some trimming action.
The time series plot can visualize measured and derived data as instant mode values or as averaged values over an arbitrary period. In addition, the difference between a long term average (10 sec to 30 min) and the instant value can be shown. A typical application for this would be the change of wind direction around an average in comparison with the change of boat course around an average. This visualizes the ability of the crew on board to take appropriate action in case of wind changes.
The maneuver estimation allows the trainer to recognize maneuvers and their qualities on a quick glance. By using the replay mode he is able to analyze the reasons by means of the recorded video and the plotted data.
The software detects a maneuver by checking changes of the sign of AWA. Additional algorithms recognize if the detected point really belongs to a correct maneuver or if they are measurement errors or hard wind shifts. The maneuver is finished when the new course is reached and the boat has reached its maximum speed in relation to the new course and wind conditions. Because of the unsteadiness of the natural environment, e.g. rapid wind changes, waves and currents, it is not possible to detect the correct start and endpoints automatically. To solve this problem the start- and endpoints are calculated with a constant time-offset with respect to the time where AWA changes its sign. A simple mechanism is available to change the constant time offset for any individual tack.
Each manoeuver is getting a rating, quantifying the quality of the manoeuver. The rating is based on the area between the VMG-curve and the straight line between the start- and endpoint. Therefore the rating is the height made good compared to the height made good in the same time without a tack.
The VMG-Plot is an instrument, which plots the velocity made good over the apparent wind angle. This instrument provides the best way to get the optimal tack angle. One conceivable scenario is that the sailor will aim for the maximum boat speed, while slowly decreasing the angle to the wind. Meanwhile the coach observes the VMG-value in the plot, where the plotted data will get a tendency like in the blue curve shown in the figure. After the sailor has passed the optimal angle it is easy read from the plot.
The PerforManD system makes it possible to analyze sail shapes during a regular training session. For that purpose additional cameras may be placed at suitable places, for example directly on deck or at the masthead. These cameras are wirelessly connected to the display unit on the coach boat. The user may remotely trigger a snapshot of the current state of the sail at any time. This snapshot is then automatically transferred to the display unit.
After the picture of the sail shape is loaded, the coach may look at it to see if the shape matches his expectations and he then is able to define profile stripes. These profile stripes allow deriving typical sail characteristics like chord length, maximum draft position, maximum draft, twist and entry and exit angles. In combination with performance data from other PerforManD plots, these sail characteristics can be used to quantify the influence of trimming on sail shape and thus on sailing performance. A measured sail with its profile stripes as well as the boat ID and recording time may be stored and therefore serve to build a database of ideal configurations for specific environmental conditions (wind conditions and direction, sea state). With input from a large number of training sessions one is able to determine a guide for optimal sail trimming for a specific crew.
All sailors need the skill to recognize wind shifts and align their course to the new wind direction, to analyze and train this skill the software contains an instrument called Wind Shifts. The delta value of the heading is shown on the left-hand side and the delta value of the wind direction on the right-hand side. The delta value is calculated based on the difference between the average and current value. In this case it is possible to use a sliding average for the average value or a constant average.
When observing a good sailor, the arrow of the HDG-delta value should follow the arrow of the TWD-delta value and the delay should be as small as possible.
Important real-time values are shown in the classical nautical instrument view. The layout is orientated on common instruments on board of a boat. This gives the user a familiar view.