2011 Volume 23 Issue 2 Pages 52-58
In order to analyze the thermoregulation system in lotus, Nelumbo nucifera, from the perspective of control engineering, temperatures of thermogenic and non-thermogenic receptacles were measured outdoors. Step response tests of lotus during the thermogenic or non-thermogenic stage, in which surrounding air temperatures were changed in a similar manner to a step function, were also carried out and receptacle temperatures were measured. The lotus thermoregulation system was subsequently investigated by analyzing the measured temperatures of lotus receptacles outdoors and of those in the thermostatic chamber. From the results, we hypothesize that lotus have a reference temperature based on a biological temperature and a thermoregulation system with a target value that is a function of air temperature. Lotus produce heat equivalent to the temperature for thermogenesis and maintain their receptacles at a higher temperature than that of the surrounding air. Thus, the lotus thermoregulation system can be expressed as a control system which inputs the deviation between the target value and the feedback value from the receptacle temperature to a controller. This controller can be expressed by integral action.