PRE2018 4 Group3

Group Members

Name	Student Id
Han Wei Chia	1002684
Niek Brekelmans	1017203
Floris Verheijen	0948592
Esmee Esselaar	0987206
Minjin Song	1194206

Problem statement

In the past few years beekeepers around the world have seen sudden dissapearances of wild and domesticated bees and a steady decline in the amount of honey bee colonies. According to research, causes of the observed decline can be found in the increase in pesticide use around the world and steadily increasing urbanization. Even climate change may be a factor that influences bee population decline.

Since around a third of the global food consumption depends on pollination by insects, of which the bee is a significant contributor, the decline or even extinction of these pollinators would have a large impact on our lives.

Besides proposed solutions to stop further decline of the bee population, there is a need to compensate the already occurred loss of pollinators. In this project, the intent is to research and design a replacement for bee pollination, in the form of a robotic and drone-like bee.

Objective

Our goal is to create a proof on concept of a drone that can collect and spread pollens of apple trees. Furthermore, we will give an advice / recommendation on how our proof of concept can be improved by making it autonomous (with image recognition) and a good way to deploy the drone with charging stations.

User, society and enterprise

Users

Due to decreasing population of honey bees in recent years, there has been impacts in beekeeping industries as well as in the rate of pollination by bees. Because significant proportion of food consumption in the world depends on pollination by insects, those who provide materials for food processors definitely needs replacements for the future. Those who are involved in food affected by pollination, such as beekeepers and large scale plant owners whose plants depend on pollination by insects, will be primary users who will definitely consider this solution to be feasible.

At this time, some beekeepers make a living by renting their bees to farms and municipalities that require more pollination. The jobs of those people will be complemented with robotic bees, so their job is saved, even if bees become extinct. Beekeepers will have to focus on repairing the robotic bee, rather than care for actual animals. If beekeepers can hande this shift in their business, they will not be affected by the robotic bee in a negative way.

Society

There are more honey bees in this world than any other type of bee and pollinating insects. This means that honey bees are the most important pollinators of our food crops. Approximately one third of our food relies on the pollination by bees. Without honey bees, we would have a global food crisis that would kill a lot of people. This food shortage in case of an extinction will be prevented if an artificial pollinator replaces bees in time. The protection of our food chain is essential and vital to humanity's survival.

Enterprise

Plants will be in trouble if pollinators die out. A lot of them would go extinct. This would lead to mass disruption of insect and wildlife life cycles. It would be hard to predict exactly what would happen, but there would be many negative impacts on user and society alike. There will be huge demand for other (Artificial) Pollination solution. Robotic bees could be the solution and be very beneficial for enterprises to invest in

Requirements

The things users will require the drones to meet are;

• The reusability of the drones
• Environment friendly materials need to be used, preferably bio degradable
• The drones need to be energy efficient so they last long enough on one charge, even though there is not a lot of battery capacity
• The flowers should not be damaged by the artificial pollination
• The drones need to be replaceable by one another like real bees are in a swarm
• The drones must be fully charged in a small time
• The drones must be able to reach a charging station in time
• The drones must hover over flowers to transport pollen for multiple flowers
• The pollen must be efficiently collected from and spread on a flower
• The drones need to be charged efficiently
• Charging should be safe
• Charging should work no matter the weather conditions

Approach

The following appraoch will be used to meet the requirements:

First a literature study will be done on the techniques and requirements described earlier. Next will be a literature study on the current state of the art of artificial pollination. We will reach out to a stakeholder to discuss the requirements of an artificial pollinator, and in what way our product would be useful for the stakeholder. When the research is done, a model and/or proof of concept will be build.

Milestones

Week	Milestones
1	-
2	Choosing a subject, define who the stakeholders are and finish the planning
3	concretely define problem and starting in-depth research into required recourses
4	Main part of research is completed Design
5	-
6	-
7	Finalize research and design Finish proof of concept Finish wiki/report
8	Present
9	-

Deliverables

• Proof of concept drone
• Advice about deployment
• This wiki

Planning

Our up-to-date planning can be found with the following link: [1].

Assumptions

For our project on robotic bees we decided to narrow down the research and design by focussing on the pollination of apple trees. This was decided since there exist around 300.000 species of flowering plant in the world, making the design a robotic bee suited for all species of flowers too complicated to achieve.

The apple tree was chosen since the apple is the most eaten fruit in the Netherlands, as well as an important export product. Furthermore, when it comes to pollination, the apple tree is self-incompatible, which means that it must be cross-pollinated to bloom. This would accomodate the testing of a prototype of robotic bee, since the self-incompatibility helps to ensure that the bee is the only pollinator.

Furthermore, since appleblossom grows all around the branches and thus also face towards the ground, the drone cannot land on all of the flowers in order to pollinate them. Therefore it was decided to focus on a drone that only hovers over the flowers while pollinating or collecting pollen.

State of the Art

PRE2018_4_Group3_Literature

Stakeholders

Philips Fruittuin

We went to the Philips Fruittuin to explain our research and ask some questions about it and the bee probem. We spoke with the owner, Carlos Faes.

• What family of apples do you produce?
  • All kinds of apples, different families of apples is good for the pollination
• Do you think the bees will be able to pollinate our food in the future?
  • Yes, I think the bee problem will solve itself eventually. Nature has a way of fixing itself. If the bee population declines by half, people will have a food shortage and die out as well. This will give the bees room to grow again.
  • People do not need to die out if farmers become more artisan.
  • People should have mutual respect for bees when dealing with them. Right now, their nectar is replaced with sober sugar water, which is not good enough for the bees.
    • It is like with insects. In the chain of food productions, insects were a problem for the farmers, so people poisoned them. Because of this, a lot of farmers produce way more food, which also means the price dropped a lot, which makes it very hard for farmers to make some money. Once the farmers kick the bucket, there is going to be a food shortage in the world and people will die. This will result in a growth of insects again.
    • If every farmer produces half of what they do now, everyone will be saved. But people are selfish and some farmers will still produce more (for the higher price), so not a single farmer will half their production.
• Do you have a method for pollination or do you let nature handle it?
  • I hire bees when the trees are flowering. I need around 20 bee colonies, which is 2 colonies per hectare and approximately 40,000 bees per colony.
  • Keeping bees myself would cost a lot of energy and time, so I do not do that. They are like pets, you need to take care of them.
• What do you think about the concept of a robotic bee / artificial pollinator
  • It would be possible to pollinate artificially, it already happens a lot in china with labourers, who pollinate using brushes.
  • It would be a shame if this would really be necessary. The problem should be solved by protecting the bees, but it is useful to research this anyway.
• Do you notice the reduction of the amount of bees?
  • Not really yet. I think I'll be dead before the beeproblem gets too serious. I do not notice much difference because this land was too big to pollinate without bees before the decline of bees, and hired bees are still easy to come by.
• How much have you thought about pollination while planting your trees?
  • I have thought about this a lot, because it is very important for the quality of your apples. There needs to be at least 30% of 'strange' pollen
• Have you ever thought about artificial pollination / do you think it is possible to create an artificial bee?
  • Read a bit about it, but I have my bees, so it is not really necessary.
  • Pollen inside of flowers is only ripe for a few specific hours, which is a different moment for every single flower. Bees can immediately notice whether pollen is useful, while a drone cannot do this easily. That is why bees stay on certain flowers longer than on others. Bees are very smart, if you can achieve to copy their ways and senses, you have build a great robot and you have found a golden business plan. This will be extremely hard to do tho.
• What would you expect from a robotic bee?
  • I would go crazy if it makes a lot of sound, like drones do at this moment.
  • Not too big
  • It should not need adjustments of my orchard (like roofing in)
• What way should be spread the pollen? From flower to flower or first collect, then spray liquified pollen
  • I do not know whether it is possible to suck out pollens out of apples, that is not my area of expertise.
  • Liquifying is probably possible.
  • If you can create specific air flows, you could pollinate through the air, but this is hard without adding a roof to the orchard.

Recommendations and Research

E-hives

When the robotic bees run out of energy, they return to their e-hive to charge. They also release the collected pollen here.

The 10x10 drone uses approx. 25W as calculated in Wireless charging possiblities and can fly around 600 seconds with a maximum speed of 7.75 m/s. As it will not fly in a straight line, but must pollinate the tree flowers in the mean while, we assume that the average speed equals half the maximum speed, 3.88 m/s. This means it can fly around 2.3 kilometers.

An e-hive needs to be able to power many drones simultaneously. If there is an e-hive every kilometer in the area, drones will not have to fly more than 2 times that distance before reaching the next hive, so 2 kilometers. This gives our drone some margin distance, so it can divert from its course a bit more for pollination and handle bad weather circumstances, like headwinds.

The 10x10 drone has a LiPo battery with a capacity of 1100 mAh.

Solar power

One of the possibilities to keep the e-hive energy efficient is to power them using solar panels. Solar panels cost quite some space. The standard solar panel has an input rate of around 1000 Watt per square meter, but you will only gain roughly 15-20% efficiency at best. A solar panel of one square meter with an efficiency of 20% will therefore be approximately 200 Watt. A day has approximately 5 sun hours, so the solar panel will produce around 1 kWh per day. This energy production depends on the weather of course. Because of this, solar power alone is not very reliable. The e-hive will still need power from other sources to ensure that the drones can always be charged. 1 kWh per day corresponds to 41.67 W, which is not enough to charge multiple drones at once.

As the e-hive are not that far apart, we will try to keep the solar panels small, which is why the solar panels will not be a lot larger than 1 square meter. The rest of the energy comes from the grid.

Pollination technique

There are 3 ways for our use case to apply pollen to the flowers. Dry pollination, liquid pollination and just by rubbing it on. I would discourage going for pollination through rubbing immediately as it is a very inefficient way of applying. From all the options, it would cost the most effort to apply and the worst results.

According to the article Artificial Pollination in Kiwifruit and Olive Trees , Dry pollination and liquid pollination are both very viable solutions. They both give very similar result if applied correctly. Except these test were applied to kiwis, but when they used the same tests on olives trees. They got similar results. Making us believe it is safe to assume that this also applies to the apple trees. Further research is of course needed for concrete evidence on this.

The way they sprayed these kiwis is quite different from how we will spray them. As they did not accurately target the flower when spraying, but instead spraying the whole tree. Wasting quite a lot of pollen. As for our use case we will spray precisely on only the flower. It is easier to accurate spray onto flowers with liquids than with a dust like substance as pollen. Making us recommend liquid pollination.

Pollen collection

Study shows that the density and length of the bees hairs is an important factor in the adhesion of pollen; the relation between the diameter of the pollen and the spacing of the bee's hairs defines the difficulty of removal. When the diameter of the pollen is significantly smaller than the spacing of the hairs, the pollen settles deeply into the hairs. However, as the diameter/hair-spacing ration increases, the pollen are suspended between the hairs, which better facilitates the removal of the pollen.

The ratio of hair-spacing to pollen diameter should be 1 for optimal pollen adhesion. However, apple pollen have an elliptic form, of on average 45 by 25 micrometer, and will therefore never exactly fit into an evenly spaced grid of hairs. Consequently, a hair spacing of 35 micrometer would be an acceptable average.

Liquid pollination

suspension consistency

When pollinating with a solution of pollen, there are several factors to take into account. Firstly, pollen are very delicate when it comes to storage. Shaking the suspension or storing it a too high temperatures causes the pollen to burst and thus become unsuited for pollination. Furthermore, the ability for the pollen to germinate, which is necessary for succesfull pollination, while being stored or suspended, depends on the treatment of the pollen. When the pollen are hydrated before being suspended, the germination rates of the pollen increase significantly. Subsequently, the composition of the suspension liquid plays an important role in the germination rate of the pollen. According to research focussed on the conservation of pollen viability in several suspensions, a solution of calcium nitrate, boric acid and CMC (sodium carboxymethyl cellulose), each at 0.01%. However, a problem that remains is protecting the pollen grains while they dry on the flower, since the unprotected drying of the suspension causes the pollen grains to lose their capability to pollinate.

pollen density

In a recent research project on the comparison between different pollination methods, a suspension of pollen in water was used as one of the studied pollination methods. For this experiment the liquid pollination was done in two days. On the first day a preparation of 1.2 grams of pollen in 5L of water was used. On the second day the pollen density was doubled to 2.4 grams of pollen in 5L of water. According to the researchers, this resulted in a spread of 3 pollen grains per cm^2 after spraying. However, this pollination method resulted in only 10 apples per apple tree, which was traced back to the low density of pollen per cm^2.

According to earlier research, a minimum of 13 pollen grains have to reach the stigma, for the plant to be able to grow a fruit. Since the stigma has a surface of a few mm^2, the amount of pollen in the solutions needs to be significantly increased.

In research into artificial pollination in kiwifruit trees, a pollen density of 12 grams of pollen per liter of water was used, along with a ratio of 50L of suspension per hectare of trees. Since this ratio of pollen per liter of water gave decent harvesting numbers, we can assume that this density is a good reference for liquid pollination. However, since this research was conducted on kiwifruit trees and not apple trees, we cannot know for sure this ratio will work for our research purposes.

Since a normal bee can carry around 15 miligrams of pollen, a density of 12g/L would mean that the collected pollen from 800 bees is needed per liter of water. If this is equated with the used 50L of suspension per hectare, the amount of pollen needed compares to the collected pollen of 4000 fully loaded bees.

Proof of concept design

Replacing functionalities

Since our objective is to develop a proof of concept of a drone attachment that will collect and transport pollents, we need to discuss how the attachment affects the performance of the drone that will carry the attachment. Because the drone will hover over apple tree flowers to collect and deliver pollens, the drone will not be similar in terms of its size, carrying capacity, and travel distances. Rather, the drones will transport pollen within the range of the charging station acting as hives for the bees and cover multiple apple tree flowers. The drones will not be able to land on the flower due to the size that is needed to carry large amount of pollent for multiple flowers.

Initial ideas

The module that will be attached to the drones will be usable for all drones that have the capacity to fly within the range of pollination. For both collection of pollens and pollination, there will be a module for each functionalities. The attachment for collecting pollens will consist of thin brushes that will surround the main frame and collect the pollens. Since the E-hive will serve as a central point for pollen collection, the brush will also be used as temporary container for the pollens during transport. The second module will comprise of a small container for storing pollen mixture and a nozzle that spreads pollens by drops. The nozzle will have holes facing towards into the flowers so that the pollens so that it sprays directly into the flowers.

Initial concept for nozzle attachment

The similar concept of nozzle can be found in medicial fields with cleaning arteries where the nozzle has holes facing different directions spraying substances that removes deposits. Since the nozzle is small enough to operate and be placed inside and cleanse arteries, this can be applied to spraying pollens inside flowers. The spraying nozzle is small and light for easy transport and low power consumptions.

References