3. Design ObjectivesDesign Objectives
• The device should be able to provide most or all of the upward force necessary to
ascend a flight of stairs.
• The device should be able to bear up to 100 kg
• The cost of the device should be comparable to that of a conventional consumer
grade hand truck
• The product should be ergonomic and easy to use
• The weight of the product should be comparable to that of conventional models
• The appearance of the product should be similar to that of conventional models
• A lightweight design
• Focus on standard house stairs
• Interchangeable toe plates
• Interchangeable- rechargeable battery
• Adjustable handle
4. MarketabilityMarketability
• Consumer stair-climbing hand truck
• Designed for end consumers to bring heavy or awkward items up / down stairs
• E.g. older people – giving families and older people ability to live a ‘normal’ enough life
with a little extra hand
– Benefit - not as cumbersome or expensive as Stair Master but ensures that they
can cart heavy or awkward objects up and down stairs easily and without the
danger of suffering dangerous or potentially fatal falls
• Small businesses or people living in apartments without the use of a lift
• Priced competitively against other ‘similar’ solutions
– Aim to make it as affordable as possible for a consumer segment, whilst aiming to
achieve the highest price that can be tolerated by the market
• Promotion through mass marketing
– e.g. advertising (TV, radio, publications targeting older generation or family
publications)
• Distribution through authorized dealers who also cater for the needs of older people
• Conduct research to determine the availability of grants available for installation
19. Chosen motorChosen motor
• Chosen motor Dongyong motors:
• With 90:1 gear ratio
• 40 RPM
• 900W optional power
• inbuilt gearbox
• fitted straight on to our product without
needing any tweak.
25. Deciding on batteryDeciding on battery
Need a 10.7 Ah. battery to run a motor of .
024kWh for 20 mins.
decided to get two 12V 5Ah sealed lead acid
battery
27. Why did we select theWhy did we select the 12V-5AH NB12-512V-5AH NB12-5
battery?battery?
• ideal size at approx. 70mm deep, 90mm
wide and 110 mm high.
• very light at approx. 1.65 kg.
• rechargeable,
• maintenance free,
• non-spillable, and highly efficient design
battery.
• expected life of 5 years in standby use
28. Variable speedVariable speed
Initial idea
•Use a variable resistor to change the
voltage.
•Theory: if the resistor is incresed to take in
extra power the speed will reduce.
•Ultimate fail.
29. The testThe test
• 200 ohm variable resistor set to 0 ohm
• Then set to 100
• Result?
• Powered off and back on
• Result?
30. The problemThe problem
• A motor is a varying electrical load.
• needs more power starting up than it does
when running.
• Also resistors waist excess energy as heat
• Inefficiency must be avoided
32. PWMPWM
• supplying full power to the motor but only
in short pulses.
• A motor takes time to respond to abrupt
changes.
• behave as if it is getting a steady voltage
33. Why PWM is perfect for us to useWhy PWM is perfect for us to use
• Effiecient
• Meets all requirement
• Easy to wire up
34. All we need to know about wiring theAll we need to know about wiring the
circuit?circuit?
• Just connect it to the
battery and motor.
36. ConclusionConclusion
• Overall good experience in terms of working in teams in the
workplace
• Design had to go through a few iterations before we were happy
– As soon as we resolved one problem, we encountered another
which needed resolution
– Good problem solving techniques
• In the end, happy with the proposed design and team believes this
product could actually sell well
37. Thank you - Any questions?Thank you - Any questions?
