Our client came to us with an idea. He had just finished a holiday in the Isle of Wight and was fortunate enough to have experienced good weather.
He found that taking his family to the beach from their accommodation on the cliff top proved to be quite hard work. They used a conventional stroller with their young daughter and as you would expect, the usual amount of child care items, clothes, provisions etc which became quite a load. Going down was not a problem, but it still took effort to prevent the buggy, child and load pulling free and careering off down the hill.
Quite the converse coming back. After a tiring day, the trek back to the hotel became quite a task, The weeks holiday became hard work and so the idea was borne. Can we attach a motor to the rear wheels was the starting question and so we started some investigation.
The design was done where two motors were proposed each driving a rear wheel. These were synchronised using an optical encoder so the speed could be controlled. There were great concerns over safety as no one will risk such a precious cargo.
We designed the system such that the motors are speed controlled and they deliver just enough power to pull the buggy along.
The handle contains a sensing circuit such that if both handles are pushed, the motors match the walking speed such that if going too fast, the force on the handles is less and the motors slow down. If the buggy tries to run away from the user, then regenerative braking is applied, topping up the battery.
If the handles are released, then the brake is applied. The more pressure applied to the handles makes more drive or braking available. If stationary, pulling backwards engages reverse.
The drive system was controlled by a micro computer using an ARM9 processor. This was housed in a small module attached to the handle.
The module included a battery status display and it can display other statistics if needed. Safety was a main concern and if the main battery became exhausted, the drive and braking system shut-down and the buggy becomes just like a normal buggy.
When powered, it still requires effort but it is like pushing when empty. We were concerned about other aspects of safety and added front and rear LED lights for use in the dark to warn other road users.
We included a security system linked to a fob carried on the person. If the buggy was stolen with or without the child, the wheels would lock and an alarm would sound when the fob was more than 3 metres away.
The basic construction includes large soft tyres and suspension to absorb shock and vibration and a fold flat system for easy stowage. We included an iso-fix seat system such that the seat can be fitted inside the car and removed to mount onto the buggy chassis.