Semi Autonomous Robotic Platform

As part of my degree I had to complete a project as part of the third year in the field of robotics and electronics. I chose to make a robotic platform, a simple idea that could be completed to a high quality with the right amount of effort. What is a robotic platform I hear you ask? well it essentially is a small buggy/rover that that moves around an assigned area completing simple jobs such as transporting goods, picking up parcels or any job that needs a moving vehicle. Usually autonomous, and very expensive, the majority of systems are very application specific. Some simple systems without any sort of control system can cost tens of thousands of pounds, and are not easy for the average employee to operate. Tackling the problem of expensive, application specific robotic platforms was the basis of my project.

4WD robotic platform
The Nexus 4 wheeled drive mecanum robot has an arduino based control system, and mecanum wheels, but will set you back $1500

Named the Semi Autonomous Robotic Platform, the idea was very simple, make a modular system, with building blocks that could be easily interchanged, and didn’t cost the world. These modules were things like motor controllers, sensors and power systems. If a user had a working platform built from this system, it would take minimal effort to swap out any of these modules to bigger motors or better sensors. This means a user can make a robot and only buy the bits they need, and even make their own modules, as long as they fit to the standard written as part of the project.

system block diagram
The initial block diagram of the system, showing how the modules can be controlled in hierarchy structure.

In most robotic systems, mainly to keep costs cheap, there is one controller that controls everything. This idea makes sense for small integrated systems that don’t need to change, but doesn’t really work when systems need to be dynamic. For instance, say you decide that your DC motors driving your robot aren’t giving you the control you want. You source some stepper motors, but this means completely changing the motor controller and therefore the software that controls it. Because one controller is in charge of everything, the software for the whole system needs to be re-written, and re-tested. That small change could have affected any of the other systems that that controller is in charge of. Make a change that breaks something important, you could set back a project weeks. This shows how painful a setup like this can be, especially when it starts to become a complex robot. Add on top of that the potential for computer intensive algorithms being used on the robot, like route planning or SLAM, and that controller suddenly has a lot to do. My system design separates these jobs out to a selection of individual controllers, such as a system specifically for motor control, or power systems. These controllers can deal with the nitty gritty hardware, and leave the master controller to orchestrate a higher level version of control.

Final Year Project
My design, near the end of the project, with the mecanum wheels, ultrasonic sensors and multiple controllers.

The added benefit of separating out all these jobs means that multiple engineers can work on the same robot, at the same time on different areas and not be worried about breaking the other person’s design. The system specification defines how the modules interact in terms of communication speeds/type, the way to alert other modules and how those communications are scheduled. The master controller (shown in the system block diagram in green) schedules all these communications and decides which modules need specific information. Warnings, control signals and user inputs are all calculated and scheduled, then communicated to and from the required modules. A power system doesn’t care that a user has pressed a button to scroll through an LCD screen, and the master controller means it doesn’t see it.

The above video shows how the robot moves with its mecanum wheels, and how it can easy move around environments. I will explain the more technical parts of the project in a later post, but this simple idea became a very heavy hardware based project, rather than the software project it started as. I learnt about mechanical design, PCB design and good techniques associated with electronic design. For these reasons, the robot won the “Best Project” award for 2017. Thank you to: Cubik Innovation for help with electronic design, and providing PCBs, VEX Robotics for donating the wheels, and Altium Designer for providing their electronic design software. I would not have been able to produce the robot I did without them.

Halfpenny Bridge: The Bridge Over Nothing

If you walk down Union street in Plymouth, just before you come to Devonport you will come across what looks like a bridge. Called Stonehouse Bridge, it comes from a time when Plymouth had a very large river/lake separating Devonport and Plymouth-Town. Originally to get across the creek to what was then known as Plymouth-Dock, you had to take the pedestrian ferry, or go all the way up to Mill bridge. So in 1767 Lord Mount Edgcumbe, who was lord of the manor of East Stonehouse, and Sir John Saint Aubyn, Lord of the Manor of Stoke Damerel, obtained an act of Parliament authorising construction of a bridge. The idea was to allow for a more direct link between Plymouth-Dock and East Stonehouse. It made sense when in the Act they described the old ferry as ‘narrow and could only be used by foot passengers’.

Stonehouse Bridge, Plymouth, engraved by W.B. Cooke 1836 Clarkson Frederick Stanfield 1793-1867

The man who designed the Eddystone Lighthouse, that now stands on Plymouth Hoe, John Smeaton, was invited to design the bridge. The bridge charged a toll to get across it, like many bridges of the time, and it was fixed by the act of parliament. It cost 2d return for a 1-horse drawn vehicle, 3d for  a 2 horse vehicle, and 6d for wagons drawn by more than 2 horses. The nickname ‘Halfpenny Bridge’ was from the halfpenny it cost for pedestrians to cross, also it was sometimes pronounced ‘Ha’penny Bridge’. Interestingly it absolved the owners from paying any public or parochial rate or tax.

The old 5 horse car at the halfpenny gate

Opened in 1773, the approach to it was via Stonehouse lane (now known as King Street) and the High Street, rather than Union Street. in 1775 the first carriages began to be hired between Plymouth and Plymouth Dock, over the new bridge. Carriages were popular but Stonehouse lane was described as ‘ruinous’ and a new road was needed. A further Act of Parliament was obtained in 1784 to create the Stonehouse Turnpike Trust. In 1815  Union Street was finally opened, as a turnpike, the users paid a toll to use the bridge, that went to the upkeep of it.  So users now had to pay for the bridge and the road leading up to it. Turnpikes were very popular in the 18th and 19th century and are basically a toll road. In 1828 the bridge was raised while Devonport hill was lowered. This meant that hackney carriages could now be used to provide a route between Plymouth and Devonport the following year.

Stonehouse Bridge from Richmond Walk.

Both Plymouth and Devonport tried many times to purchase the gate, but the bridge, along with Stonehouse Mill bridge were sold in February 1890 to the General Tolls Company Ltd for £122,000. The company (with the Earl of Mount Edgcumbe and Lord Saint Levan had shares in) was registered on February 12th 1980. The idea was for the owners to collect the tolls rather than auction them, which was more common at the time. From October of 1917, servicemen and nurses could get across the bridge for free.

Stonehouse creek before being filled in, from the bridge

After long negotiations, an Act of Parliament in 1923 allowed Plymouth Town Council to buy the toll rights for £100,000. This meant that the Council could have charged tolls and collected than money for up to ten year. Instead, on April 1st 1924, the Mayor, Mr Solomon Stephens, and council visited all the toll houses and declared them free.

Stonehouse Bridge Freeing Ceremony, 1924 looking towards Devonport. From a postcard

The upper end of the creek, near the Pennycomequick, was known towards the end of the 19th century as Deadlake. St Barnabas Terrace, a road now adjacent to the park, was marked on 19th century maps of the area as Deadlake Lane. Toward the end of the 19th century, culverts were made to channel the streams that ran into deadlake, and the swampland was filled in with rubble from the quarries at Oreston and Cattedown. To celebrate queen Victoria’s reign, Victoria Park, along with the park-keeper’s lodge, was formally opened to the public in 1903.

Looking down the filled in fields, towards Stonehouse

Between Mill Bridge and Stonehouse Bridge, the creek was filled in in 1972, when 600,000 tons of ballast and rubble were used to create 19 acres of land. Now a set of pitches for Devonport High School for Boys (previously the royal naval hospital) and the pitch for Devonport RFC. When you walk along it you can see some areas, especially close to the bridge where all the rubble has been added. On the water side of the bridge you can see where the arches have been filled up. Stonehouse bridge is now more of a dam, but one with some important history for Plymouth.

Halfpenny Bridge, on the side of the creek

Plymouth Castle

So as we discussed in a previous post, Plymouth wasn’t always the power that it is today. In fact, in 1066, during the norman conquest, it was still called Sutton Pool, and had a population of 18 people. So realistically, there was no real need for any sort of fortification. The only place with a need for protection was just up the river at Plympton. Here, there was a Motte and Bailey Castle. Basically a small keep on top of a big hill, surprisingly effective at the time.

Over time though, the river changed, and the need of Sutton as a main port suddenly became of strategic importance. Around the start of the hundred years war in 1337 it was attracting unwanted attention from continental forces. It’s thought that earthwork defences were built around this time on the hoe and waterfront. There was also likely to have been similar works on the other side of the river at mount batten.

The most important part of this defence was Plymouth castle. In 1377 a murage grant was received, this is basically a tax specifically for castles, walls and other defences. The exact date that it was built is unknown, but it was first recorded in the early 1400’s. The castle was on the western side of Sutton Pool. It had 4 sides, with round towers on each corner, with curtain walls, 4 meters high. The main need for the castle was to control a chain that was raised to stop access to the harbour. If a ship got caught in this, it would be subjected to the castle’s cannons. The castle’s entrance was shielded by a barbican, which now lends its name to a part of the city.

There is no official date that the castle is said to have been built, but based around events we can give a good range. In 1340 during the Hundred Years’ War, the town was attacked by a flotilla of french raiders. Although they burned a manor house, and took some prisoners, they failed to get into the town. It was said to be due to an effective defence, this could be the castle, or it could just have been earthworks. There was another attack by the french in 1377. This lead to the murage grant to fund fortification, this may well be the money used to build the castle, but it could also have been used to fund walls or earthworks.

In 1400, it was likely that the castle was in existence, as it allegedly drove off a fleet of french ships. It was said that an english force of ships were being pursued by James of Bourbon, Count le Marche. The english forces sought refuge in Sutton harbour and scared them away. In august 1403 the castle was definitely present, and provided refuge when a Breton army landed at Cattewater and attacked and burned the town. This attack is still remembered today, by a part of the town known as Bretonside. This is the point where the invaders were stopped by the citizens marching out from the castle to attack them.

After this the castle saw very little real action. Other parts of the city were being fortified, and the castle became less important in the grand scheme. In 1549, it did play a part in the Prayer Book Rebellion; where cornishmen rebelled against the law created to have all church services in the land to be conducted in the english language. The Cornish at the time rarely spoke english, and so a rebellion started. At a point during this time, the town was besieged by rebels. The town quickly surrendered, but the castle didn’t, it held members of the crown and protestants, likely targets by the rebels. Eventually the rebellion was defeated, and the siege was lifted.

In 1588, the castle played a small part in the attack on the Spanish Armada. The English Navy took shelter from the wind and waited for the tide in Sutton harbour. The Castle gave the Navy a good defence. Unfortunately after this, in the Elizabethan era defences had moved on from simple castles. Sir Francis Drake (kinda famous in Plymouth) built an artillery fort on the Hoe. The structure, eventually known as Drake’s Fort was partially built using stone from Plymouth Castle. After this the closest it got to any action was during the civil war, when it held a parliamentary Garrison. Although, because Royalists controlled Mount Batten, Millbay on the west side of the harbour was used over Sutton Harbour so the castle wasn’t used as a military structure.

That is basically the History of Plymouth Castle. The castle itself eventually fell into disrepair, actually described as ruinous. It was used as a prison, and also a workhouse for a time. Unfortunately, in the 19th century, during the population boom, the remains were slowly robbed to be used in houses and other building projects. There is only a small part of the gatehouse still existing, and it has been turned into a part of a garden.

castle gatehouse
The remnants of the Castle Gatehouse
castle gatehouse
The remnants of the castle gatehouse, and the building development behind it
garden in the castle
The garden set into the old gatehouse

Fun fact: the four towers of Plymouth Castle are said to be remembered in the towns coat of arms, with 4 towers separated by st. Andrews cross (the patron St of Plymouth). The towers are said to be protecting him.

plymouth coat of arms
Plymouths Coat of Arms on a JaJa Postcard in 1925

The Golden Hind

A famous person in the history of Plymouth is Sir Francis Drake, i’m sure many of his expeditions will make it into this section of my blog in the future, but today we are going to talk about a famous ship that he sailed, the Golden Hind.

So in 1577, Queen Elizabeth chose Francis Drake for the most daring challenge of the day. To lead an expedition, passing through South America via the Strait of Magellan. Exploring the coasts that lay beyond it. Before setting sail, Drake met the queen face to face for the first time. She reportedly said “We would gladly be revenged on the King of Spain for divers injuries that we have received.

Why was this important? Well this basically meant the queen backed him. He had official approval to benefit himself and the queen (the queen had shares in the expedition). On top of this he was told to cause maximum damage to the Spaniards. The problem was, Drake took this too far, and acted more like a privateer. They weren’t to know at the time, but this would eventually lead to the Anglo-Spanish war.

He set sail in December 1577, with 5 small ships with a total of 164 men manning them. Reaching the coast of Brazil in early 1578. Note at this time, Drake’s flagship was named the “Pelican”, and it was small only displacing around 100 tons. Mid way through the journey, Drake had the inspiration to rename the ship the “Golden Hind”. Named after his patron (the man who payed for most of it) Sir Christopher Hatton; who was at the time, one of the queens favourites. His crest was a Golden ‘hind’, another word for a female deer.

The date that made the Golden Hind a big name was the 1st of March 1579, when they were in the Pacific Ocean, just off the coast of Ecuador. The ship challenged and captured a Spanish galleon. Named Nuestra Señora de la Concepción the galleon had the largest treasure ever captured up to that date, at over 360,000 pesos. The six tons of treasure took 6 days to move between ships.

Why is Plymouth important in this story? well it is the first harbour that the ship sailed into when it got home, on the 26th september 1580, a famous day in Plymouths history. Note that of the 80 people the ship left with, only 56 were left aboard.

Even though Drake basically acted like a pirate, the Queen herself went aboard the Golden hind when it sailed to Depthord in the Thames Estuary. There Drake got bestowed with a knighthood, and went into the history books. What did the queen get, around £160,000. This was reportedly enough to “pay off her entire foreign debt and still have £40,000 left to reinvest. The return to all the investors came to £47 for every £1 invested, or 4700%, a good return in anyone’s book.

What happened to the Golden hind in the end? well it basically stayed in Deptford. Maintained for public display, incidentally the first ship to be kept and displayed in this manner because of the historical significance. It remained there for around 100 years, and eventually rotted away and was finally broken up. It’s still not gone or forgotten though, parts were reportedly made into a table in Middle Temple Hall in london, and a chair in Buckland Abbey in devon, also the Pelican Inn in Gloucester claims to be made with some timbers from the ship.

 

My First Post About Plymouth – The Early Ages

So I have been living in Plymouth as a student for the past few years, studying at Plymouth University. It’s a great place, but I realised I don’t really know anything about it, or it’s history. So I have decided to start finding it out. I intend to post all the interesting stuff I find out here on my blog.

Where better to start that.. well the start! Or at least as far back as is recorded. The early history of the Plymouth area.

There have been many excavations and archaeological digs conducted over the years, with one of the most notable by Barry Cuncliff in 1988. During excavations in local caves in the Mount Batten area, Homo Sapiens were found, along with artefacts dating from the bronze age through to iron age. According to Cuncliff, this shows that it was one of the main trading ports of the country at that time. He goes on to state that Mount Batten was the site of the earliest trade with Europe yet discovered in bronze age Britain.

Ptolemy’s Geographia talks about an unidentified settlement named “TAMARI OSTIA” which translates to mouth/estuaries of the river Tamar. This could be the the location of the modern city of Plymouth, it could also be Mount Batten, or even potentially the settlement of Plympton just up the river.

The modern name of Plymouth is thought to have come from the fact it is at the mouth of the river  Plym. Just up the river is the old town of Plympton, was recorded as Plymentun circa 900. There are many theories about where this name comes from, some say its from the old english word for “plum tree” (ploumenn). Other theories include the Latin for tin (Plumbum), or the Cornish word for lead (Plomm). All we know is that the first recorded name for the river was the Plyme in 1238. About this time are the first recorded name of Plymouth as a settlement (Plymmue in 1230, and Plimmuth in 1234). Previous to this though, and area known as Plym Mouth was noted in a Pipe roll in 1211. 

Plympton was at one point an early trading port, up until around the early 11th century, when the river became very silted, and forced merchants and mariners to trade instead in modern day Plymouth, around the area of the Barbican, much closer to the rivers mouth. At this time there was only a village there called Sutton, an old English word meaning “south town”. Although the town has been mentioned in many documents, Plymouth officially replaced the name Sutton in a Charter of King Henry VI in 1440.

I hope you find my first post about Plymouth informative, and interesting. I plan on doing quite a few of these posts, comments would be appreciated, and ideas that people want would also be great. Thanks for reading.

We are Making a Foundry!

So the new term of university is here, and we have a couple of weeks to settle into our new house. As a house we felt we needed a big project to get us going, to inspire a bit of teamwork in us, and we think we have found it! After seeing this video by Grant Thompson, we have been inspired to make a similar forge. So, over the next couple of weeks, this is what we will be making. As much as this will be a little homemade enterprise, we should be learning about business skills, basic accounting, and some safety stuff along the way; so it wont all be fun! The idea is to achieve, maybe inspire, and to make something that works, but let’s just see how this ends up.