The First Control Engineer

Engineering was not a recognised discipline in the ancient world and only gained that distinction towards the end of the 18th century. One of the first people to be recognised as an Engineer was James Watt, the inventor of the steam engine. In fact both of these claims are inaccurate, he was a mathematical-instrument maker by profession and he did not invent the steam engine since crude steam engines had already been in use in England for some forty years. His contributions were to make the inventions that turned the steam engine into a cost-effective power source.

As a graduate of the University of Glasgow I must also insert a 'plug' here. The steam engine was developed in the workshops of the University of Glasgow, which became a centre for engineering studies well over 100 years before Cambridge got round to the subject. It's also worth pointing out that the University of Glasgow was founded in the 15th century and is therefore nearly as old as Cambridge. dgi

James Watt was born in Greenock, (a town on the estuary of the river Clyde, some 30 miles downstream from Glasgow). His father owned a ship and house building business and was a local magistrate and the treasurer of Greenock Town Council - clearly an important local citizen. Watt was a delicate child, initially educated at home, but later he entered the local grammar school and received the standard education of the time, including Latin, Greek and Mathematics. However, he was also interested in his father's workshops, and was provided with his own workbench there, where he made his own models, including a barrel organ and copies of ships instruments. At the age of 17 he decided to become a mathematical-instrument maker and moved to Glasgow where one of his mother's relatives worked in the University.

After completing his training, in 1757 is set himself up in business as an instrument maker and opened a shop at the University. He became acquainted with many of the scientists at Glasgow University, in particular, Joseph Black, who had developed the concept of latent heat. In 1764, while repairing a model of a Newcomen steam engine he realised that much of the heat input was lost in the latent heat of its exhaust steam. This led to his invention of the external steam condenser, which transformed the steam engine into an efficient source of power. He became involved in the development and exploitation of the steam engine, first with John Roebuck and later with Matthew Boulton, the owner of the Soho Works in Birmingham. Watt finally moved down to Birmingham to join Boulton.

However, our interest centres on Watt's later invention of the centrifugal speed governor for his steam engines. This consists of a couple of steel balls attached to a vertical rotating shaft. Two further links connect the balls to a sliding collar on the shaft, which in turn is linked to a vertical rod which leads to the valve controlling the steam input to the engine. Clearly, as the engine speeds up centrifugal force causes the balls to move outwards, which in turn moves the rod and reduces the steam input to the engine. Thus an equilibrium point is reached at which the engine settles down to a more-or-less constant speed.

This was the first clearly identifiable control system for a mechanical power source and represents the starting point for serious development of control systems. It also represents the point at which it started to become apparent that there was more in this subject than meets the eye. It was soon found that this sort of control could become unstable, leading to continual 'hunting' of the speed of the engine rather than a process of settling down to a steady speed. A true understanding of this sort of behaviour was, however, still in the distant future, and the early engines used crude empirical methods to stabilise their operation.

The First Control Engineer - James Watt