icadi
GOLF TROLLEY FEASIBILITY REPORT
Duncan Macmillan
Table of Contents
1
The Trolley....................................................................................................................................... 2
1.1 Requirements.......................................................................................................................... 2
1.2 Approach ................................................................................................................................. 2
1.2.1 Mechanical ...................................................................................................................... 2
1.2.2 Electronics ....................................................................................................................... 3
1.2.3 Control Strategies ........................................................................................................... 4
1.2.4 Software .......................................................................................................................... 5
1.3 Conclusion ............................................................................................................................... 5 Following the user........................................................................................................................... 5
2.1 Requirements.......................................................................................................................... 5
2.2 Problems and Potential Solutions...........................................................................................6
2.2.1 What if the trolley gets stuck? ........................................................................................ 6
2.2
1 The Trolley
This section of the document will give an overview of the trolley from a technical perspective, including the mechanical and electrical requirements. This section also contains a summary of capabilities that are expected from the trolley to be successful in the target environment - that being the golf course.
1.1 REQUIREMENTS
Must be able to perform well in a golf environment, with consideration of the: o Terrain
o Weatherconditions
Must be able to withstand local hazards such as: o Hit from a golf ball
o Hit from a golf club o Dirt
o Water
o Sand
Must be able to carry a load of up to 25Kg
Must be able to remain upright and balanced under maximum load
Must be able to achieve speeds of at least 6km/h under maximum load
Must be able to cover an 18-hole golf course which is:
o approximately8.5km. o Around 4 hours long.
1.2 APPROACH
The design of the trolley in not yet finalised; It is however, loosely based on the design of a Segway.
1.2.1 Mechanical
The electrical system is centred on the battery and the distribution of the battery voltage and current to other subsystems. Since the battery for this kind of vehicle contains a lot of energy it is necessary to monitor the operational status of the main electrical system, and have safety features to turn it off in case of an emergency or malfunction. The safety measures in this system will consist of fuses, a power management system and a failsafe mode.
1.2.2.1 Battery
The battery will have to be selected to fulfil the goal of being able to cover a full game of golf on one charge as well as provide sufficient torque to keep up with its user on a variety of terrain. It would be beneficial to choose a battery that features a continuous discharge current, and an internal management system if available to simplify the integration of the battery into the electrical system.
A charging port for mobile devices can be integrated into the design, or alternatively to save on battery power, a solar panel can be fitted for that purpose.
1.2.2.2 Main processor board
The main processing system is the most complex module. It works as the communication hub between all the other software systems and has the responsibility to answer to all communication events.
It is also responsible for gathering and converting all sensor information to a format usable by the control system, and to run the control loop.
1.2.2.3 Power Management Board
The purpose of the power board is to monitor the battery and distribute the power to the different subsystems. The main goals for this board are to warn the user of low battery voltage, estimate the state of charge in the battery, measure current flowing from the battery, and contain some safety features which will be outlined in the following section.
1.2.2.4 Sensors
An accelerometer is fundamental. These sensors may be built in numerous different ways. In modern applications where low cost and small size is important, the microelectromechanical system (MEMS) type accelerometers present a feasible option.
A modern accelerometer often includes a spring-loaded structure whose deflection in response to external forces can be capacitively sensed and converted to an electrical signal.
Another crucial sensor, the gyroscope, is used to measure the angular rate of an object with respect to an inertial system. They are commonly of MEMS type like the accelerometers if a low cost and small size is desirable.
Both of the sensors have some drawbacks. While the accelerometer can give the absolute reference of the pitch angle when unaffected by other accelerations other than gravity, it will also give a misleading output when affected by accelerations.
The gyro output signal can also be integrated to find the angle of the motion. This estimate will be less affected by linear acceleration than the accelerometer output, but will suffer from drifting when numerical integration is used.
Knowing the properties of these two sensors, smart filtering can be used to fuse the outputs and attain a better estimation of the angle. A filter commonly seen in hobby applications is the ‘Complementary filter’. This is a simple filter which demands very little processing power and is simple to implement. The filter basically uses the gyro for short term estimation and correcting this estimation based on the accelerometer’s absolute reference of the gravity.
1.2.2.5 Safety
The most important design parameter for the main electrical system is the current rating and the safety measures. All components and cabling have to be selected to continuously withstand the ampage output by the battery.
The power board mentioned earlier is responsible for controlling relays to distribute power to other subsystems and shut down the motors when a malfunction is detected. It is also responsible for allowing charging only when the correct voltage is applied.
The failsafe mode mentioned earlier is there to turn off a relay that cuts the power to the motors. In this way, if the vehicle loses connection to the user, it cannot continue to drive, which otherwise could result in collisions with other people or objects.
Fuses would be mounted between the battery and the main switch to limit the current in case of a severe short circuit failure in the vehicle.
An on/off switch is a standard addition allowing the user to turn the trolley on and off when required to save on battery power.
1.2.3 Control Strategies
The trolley will simply tip over if not controlled. Naturally the first objective of the controller must be to prevent this from happening. The second objective of the controller is to make the rider able to control the speed of the vehicle.
1.2.3.1 PID-controller
The PID-controller is by far the most commonly controller used today. It tries to minimize the error between the reference signal and the actual output signal. It is often implemented with some extra functions to make it more realizable in a practical implementation. It also controls relays related to charging to make sure the trolley cannot drive while being charged.
1.2.3.2 Motor driver
A powertrain system enables the propelling and control of the vehicle. It is paramount to have a strong powertrain that can handle bumps and rough terrain, with low backlash in the driving mechanism. Too much backlash can introduce oscillations in a control system and make it harder or impossible to control.
The powertrain makes it possible for the electric motors to propel the vehicle. It is defined as the base plate with the motors, gearbox and wheels.
1.2.3.3 Wheel sensors
After examining existing systems, an efficient sensor system is composed of two encoders, one mounted on the motor axis of each motor and a circuit board with a processor dedicated to decoding the encoder signals. This processor would then send the decoded information to the main processor over serial communication.
A counter has to be connected to a data register using an event system. It’s important to choose a processor that supports such an event system. The register value increases or decreases when the encoder is turning clockwise or counter clockwise.
1.2.4 Software
The software in this sort of vehicle would run on different processors depending on the task it performs. This makes the system modular which reduces complexity during software design and facilitates easy troubleshooting and system replacement. These benefits come at a price: the need for communication between the processors.
The most critical software runs on the main processor system as previously mentioned, running a real time operating system such as FreeRTOS that would provide all the necessary software as well as being free to use.
1.3 CONCLUSION
To design and build a golf trolley matching similar commercial options, requires significant research and design. There are many areas which require domain expert with an engineering background and some knowledge of control theory and real time control systems.
A strong knowledge of dynamical system is also necessary such that the hardware could be designed to be controllable from the start.
It is definitely feasible to construct such a trolley that covers all requirements mentioned above, but the development costs will be considerable due to requiring a set of individuals with different skill sets.
2 FOLLOWING THE USER
One of the major selling points is the ability for the golf trolley to autonomously follow its user around whilst carrying a load (i.e. a bag of golf clubs). This presents several technical challenges that have to be solved in order to provide a solution that sufficiently meets the requirements of the trolley, and one that is safe for the user.
2.1 REQUIREMENTS
Safely follow the user with minimal input from them.
Keep a set distance away from the user to stop the trolley from interfering.
Ignore other users and trolleys on the golf course.
Allow the user to approach the trolley without it running away.
2.2 PROBLEMS AND POTENTIAL SOLUTIONS
2.2.1 What if the trolley gets stuck?
When thinking of a golf course, it is expected that it has a well-maintained lawn and mostly flat terrain. The trolley shouldn’t have a problem with this kind of terrain. What needs to be considered is that golf courses also contain sand pits and occasional hills, both of which can be a potential problem for the trolley to get across.
It’s important for the trolley to almost “understand” its capabilities to stop the trolley from, for example, indefinitely trying to climb a hill that is too steep for the motors; which could in turn damage the trolley.
The safest solution to this problem as mentioned in the previous section of the document is to simply stop following the user.
2.2.2 How to make the trolley simultaneously keep distance but also allow the user to approach itself?
In a golf game scenario, the user requires a bit of personal space to concentrate and make the swings. The trolley has the be prevented from getting in the way because it would immediately become a nuisance.
One of the solutions is to program the trolley to keep at a certain distance away from the user and allow the user to disable this behaviour at will using his control device. The con of this solution is that it requires the user to remember to stop the trolley from unintentionally running away.
The other solution to this problem would be to allow the trolley to only move forward, allowing the user to approach the trolley when necessary and allowing the trolley to catch up with the user with no interaction. This solution does pose a problem, however. In a scenario where the user moves away from his position with the intention to come back, the trolley might want to catch up and get in the way of the user.
2.2.3 What if there’s something between the trolley and the user?
This is an important safety consideration, although the distance between the trolley and the user might be small enough to significantly reduce the likelihood of something getting in-between. Equipping the trolley with a short-range sensor is something to consider to make sure it doesn’t bump into anything.
2.3 APPROACH
There are a few wireless solutions that could be used to keep track of the user, the trolley and the distance between them. The pros and cons of each solution are outlined in this section.
2.3.1 GPS
GPS is one of the most widely used systems for positioning worldwide. “Positioning” is in the name after all and there are similar products already on the market using GPS as the main tracking system, which makes it a clear consideration for a system such as this one.
The way GPS can be utilized to fulfil the requirements is to place a GPS module on the trolley and a another one in the control device the user is carrying. Using a Bluetooth connection, the device in possession of the user would automatically send its position to the trolley which in turn would compare, then calculate the path and distance to travel.
While this sounds good in in theory, there are certain problems in practice that could prevent this approach from being viable. GPS errors are fairly large. This of course depends on many factors such as the weather and location. This can be especially observed indoors where even with a stationary GPS receiver, localisation data can have a tolerance of up to tens of meters, merely estimating the real position.
While outdoor tracking will be better, it might not be consistent enough for this approach to be appropriate as of now. This might change drastically within a few years however. Galileo - a global navigational system is being developed by the European Union and other partner countries. It began operation in 2016, and is expected to be fully deployed by 2020 and is reported to be accurate up to 1 meter.
2.3.2 Ultrasonic
An alternative to the previous approach is to use ultrasonic beacons as a transmission method. Similarly to the GPS approach, both the user and the trolley would require to carry a beacon but instead of using Bluetooth to transmit data for calculating distance, Ultrasonic beacons would work on a basis of signal strength.
The output amplitude is directly proportional with the actual distance to the beacon. This allows for the trolley to know how far away it is from the user. For increased accuracy multiple beacons can be placed on the trolley, an algorithm would rotate the trolley until it detects a maximum level of signal (that being the user) at which point the trolley can approach until the detected signal reaches a given threshold.
This threshold would be used to keep the trolley at a set distance away from the user. An infrared signal can be used to further enhance the accuracy of the trolley.
There are of course some drawbacks of using this approach. First and foremost, the signal can reflect away from surfaces which could potentially confuse the trolley. This issue can be fixed by placing beacons around the trolley, giving it a way of detecting the signal regardless of where it’s facing and if a certain receiver is blocked.
2.3.3 Bluetooth
Looking back at section 2.3.1, another valid option is to use Bluetooth on its own as opposed to combining it with GPS. In this approach, the trolley would require a Bluetooth sensor on each side and one sensor in possession of the user. The trolley would use its two sensors to essentially triangulate onto the position of the user, using the difference in signal strength between the sensors to determine the rotation, much like ultrasonic sensors would.
This approach has already been utilised in an existing commercial product with similar function to a varying degree of success. Many users of this product have experienced problems with the trolley not following them or the trolley bumping into their ankles. This could be a problem with the technology itself not being fit for purpose or it could simply be a bad execution.
The one advantage that this approach has over ultrasonic sensors, is that Bluetooth has a much better range of up to 100 meters.
2.4 CONCLUSION
After some extensive research, a few other potential tracking solutions were found, however, none of which were suitable for the purpose. In addition to that, a majority of the sources and similar projects that were found, favoured a combination of ultrasonic and infrared sensors thus suggesting that this is the most optimal solution at this time.
A GPS system, especially with the Galileo global navigation satellite system reaching its full operational capability soon also sounds very positive.
3 USER DEVICE
The user is required to have a simple device that allows a good degree of control over the trolley. In addition to that, the device should have the ability to record data used for calculating various statistics on shot distances and power to provide the user with valuable feedback for training.
3.1 REQUIREMENTS
Must be small enough not to distract or affect the user and his performance
Must be able to collect appropriate data for training
Must be able to connect and control the trolley remotely
Must be able to show trolley’s battery level and other valuable information
3.2 APPROACH
There have been a few design ideas taken into consideration with the aim to cover all requirements while keeping the device as low-profile as possible.
3.2.1 Remote
The simplest solution is to create a remote-control style device that the user can put away into their pocket and take it out when convenient. This idea was quickly dismissed as it posed many problems in the areas of collecting data.
A device such as this, while placed inside a pocket has very limited options regarding data collection especially when the aim is to calculate shot statistics.
3.2.2 Bracelet
A slim bracelet would be a very stylish addition to the trolley. Not only that, but data collection would also be very easy as a set of sensors could collect data directly from the movement of the arm. The trolley could be controlled by a few small buttons alongside a small display, or alternatively the bracelet could take form of a device reminiscent of a smart watch, featuring a small touchscreen.
The cons of this approach are that not all players might like the idea of having something on their wrist whilst playing. Some players might have their wrists occupied already which also creates a problem.
3.2.3 Lanyard
A small device on a lanyard is one of the ideas that were considered. This would allow for a good degree of choice between sensors that would collect relevant data as well as keeps the users hands free.
This idea, however, was also dismissed when looking that it from a gameplay perspective. The device, although small and light, would swing with the movement of the user likely creating a distraction or getting in the way.
3.2.4 Pager
Expanding upon previous ideas and taking in consideration the cons of each, a pager-like device provides a good middle ground under the aspects of functionality, usability and keeping a low profile.
Such a device could be clipped onto the belt of the user from where the user would have easy access to the control features for the trolley as well as the ability to un-clip the device to view the screen.
Granting all this, the device requires a lot of thought on the best way of collecting data that can be used in aiding the user. Much like the remote control, the user might decide to place this device inside a pocket where data collection is difficult. The small nature of a pager also poses a higher risk of being lost compared to other approaches.
3.3 CONCLUSION
In conclusion, there is a number of ways to integrate all the required functionality into a portable, personal device. Looking back at the pros and cons of each approach, the bracelet and the pager appear to be the most viable options so far.
These two approaches provide the most flexibility in collecting data which is after all a major selling point.
4 COMPETITORS
This section of the document covers the top competitors to this trolley. Each competitor’s trolley is summarised and analysed to give a good comparison of their features.
4.1 STEWART GOLF X9 FOLLOW
Whilst conducting our research, we discovered there is already a golf trolley with a ‘Follow Feature’ available on the market called the Stewart Golf X9 Follow Review.
This is the only trolley on the market which follows you around. A unique Bluetooth design explained in section 2.3.3 lets it follow you around the course, turning when you turn, stopping when you stop, and removing the need to steer it with a remote control, although this is still an option.
Many of the features of the X9 Follow have already been discussed in section 2 of the document such as a dead zone around the trolley, preventing it into bumping into the user. Something to note here is that the X9 Follow does not have any form of obstacle detection which forces the user to bring the device into a manual remote-control mode to overcome them.
The X9 Follow has received mixed reviews from their users. Some very happy with all the features while the negative reviews mostly point out that the follow mode doesn’t work as intended however they’re still mostly happy to use the trolley in remote control mode.
In addition to the Stewart Golf X9 there are a number of remote-control electric golf trolleys currently on the market, but none of these trolley’s have a ‘Follow me’ feature.
The Stewart Golf X9 Follow retails at £1499.00.
4.2 MOTOCADDY S5 CONNECT
The S5 Connect trolley is one of the most popular choices. While it doesn’t have a “Follow me” mode, the main focus/selling point of this trolley is its ability to integrate with the user’s phone.
By allowing the user to see his messages, emails and missed calls, the trolley offers a more focused golfing experience. The phone application that comes with the trolley contains information for 40,000 golf courses. This information is used along with the GPS module installed in the trolley to offer front, middle and back distances to the green along with par of the hole, plus a clock and a round timer.
Other than holding the golf bag and being motorised, the S5 Connect doesn’t share other selling points with the proposed trolley which is an advantage; offering a potential customer a whole different golfing experience.
The Motocaddy S5 Connect retails at £549.99.
4.3 BIG MAX COASTER QUAD
In comparison to other trolley on this list, the Big Max Coaster Quad is the least technologically advanced. Where it lacks in technology the Coaster Quad makes up in convenience, featuring many helpful Accessories, such as Umbrella holder, Scorecard holder, drink holder and an optional seat.
The trolley also features swivelling front wheels to improve manoeuvrability and an optional solar panel for charging mobile devices along with a phone holder.
The lack of assisting and tracking technologies on this trolley suggests that this trolley has been designed for rather casual players who want an electric trolley with minimal fuss, aiming to simply provide a convenient solution to regular tasks.
Coaster Quad is highly rated mostly due to its stability and good performance on hilly terrain. The Big Max Coaster Quad retails at €1,199 (£1,081.61).
4.4 POWAKADDY FW7S GPS
Set side by side to the Motocaddy S5 Connect, both the design and the list of features are very similar. Featuring full GPS capability and display, much like the S5 Connect as well as being preloaded with 37,000 golf courses to allow for various distance measurements.
The major difference between the two is that the entire system is all integrated into the trolley itself along with a much higher quality display, removing the phone from the equation.
The PowaKaddy FW7s GPS retails for £699.
5 OVERALL CONCLUSION
This project isn’t a small undertaking. The technologies that are required to provide the user with all the functionality this golf trolley is aiming to give exist and are available, along with all the hardware and electronic components.
REDA