Abstract: The present invention provides a sequencing control strategy for environmental system controllers that takes better advantage of the capabilities of the system elements to enhance performance and reduce operating costs. Digital controller technology is included and operates in accordance with a state transition diagram clarifying conditions that must exist for the environmental controller to switch from one mode of operation to another (e.g., from a cooling mode with dampers set at the minimum position to a cooling mode with the dampers modulating to reduce the energy used for mechanical cooling). Several controllers, or a single controller operating on several sets of control parameters, sequentially operate in accordance with transition data and system performance characteristics for controlling system operation.

Abstract: A closed loop feedback control system that operates to maintain a process variable at or near a process variable setpoint. The system includes a setpoint regulator that adjusts the value of a process variable in response to a setpoint associated therewith. A sensor associated with the setpoint regulator senses the process variable and outputs a process variable signal corresponding thereto. A controller connected to both the setpoint regulator and the sensor in a closed loop is programmed with PID logic to control operation of the setpoint regulator in response to the process variable signal received from the sensor. The controller generates a control signal that controls the setpoint regulator based on a non-uniform two-point sampling of the process variable signal. The controller delivers smooth, bump-free, control in spite of changes in the setpoint controller gains or system parameters.

Abstract: A control system for controlling an air handling unit. The control system links the position of an exhaust air damper and a recirculation air damper so as the exhaust air damper is opened, the recirculation air damper is closed the same amount, and vice versa. An outside air damper remains completely open at all times. The relative positions of the exhaust air damper and the recirculation air damper control the amount of outside air that is emitted into the air handling unit through the outside air damper. For each of the control states of heating with minimum outside air, cooling with outside air, mechanical cooling with maximum outside air, and mechanical cooling with minimum outside air, the outside air damper remains completely open, and the position of the exhaust air damper and the recirculation air damper are controlled based on a particular state. Sequencing strategies are employed for transitions between the control states that utilize these positions of the dampers.

Abstract: A feedback controller configured to automatically tune a control system by determining proportional gain, integral time and/or derivative time control parameters based on estimates of process time delay, process time constant and process gain values which are monitored by the feedback controller. The feedback controller further determines control limits for estimating the process time delay based on the resolution of the sampled values of the process output and the standard deviation of the process output during the initial steady-state condition. The feedback controller also estimates characteristic areas for a first-order response based on a first-order plus time-delay model to determine process time constant and process gain values. These process time constant, process gain and process delay estimates are translated into proportional gain, integral time and/or derivative time control parameters based on design relations of the particular feedback controller.

Abstract: The present invention relates to a diagnostic system for use in a network control system. The diagnostic system is preferably utilized to analyze VAV box performance in an environmental control system such as a network facilities management system. The diagnostic system advantageously records temperature, airflow, and actuator position data in the controller associated with the VAV box. Such a system allows person to analyze VAV boxes and controller performance over a particular timely period and the lifetime of the system. Box and damper warnings may be provided by the diagnostic system when the box or damper is operating below particular performance levels. Preferably, the diagnostic system formats the air flow actuator positions and temperature data so that it can be displayed for graphing. The diagnostic data is advantageously stored in the individual controllers.

Abstract: A pattern recognition adaptive controller configured to dynamically adjust proportional gain and integral time control parameters to minimize integrated absolute errors between a setpoint temperature and a monitored temperature in an HVAC system. The pattern recognition adaptive controller receives a sampled signal representative of the temperature and determines a smoothed signal based on the sampled signal. The controller characterizes a disturbance in the smoothed signal by a damping factor and a closed loop response time. When a significant load disturbance or setpoint temperature change occurs, the controller estimates an optimal gain based on the damping factor, and an optimal integral time based on the response time. The estimated optimal gain and estimated optimal integral time are used to determining a new gain and a new integral time values, to which the control parameters of the controller are then set.

Abstract: A load shedding apparatus for limiting peak electrical demand in an electrical system to a target level through load shedding. The apparatus employs predictive control logic to estimate the amount of energy that needs to be shed in a predetermined future period. Preferably, the load shedding apparatus forecasts the amount of energy require in a predetermined future period by analyzing current energy consumption, current load shedding, and error factors indicative of the random energy demand characteristics of the electrical system. The apparatus estimates the amount of energy that needs to be shed in view of the forecast of the amount of energy required in the predetermined future period. The apparatus selects non-essential loads for shedding until the estimated amount of energy that needs to be shed is reached. The apparatus transmits shed control signals to selected devices within the electrical system to disconnect the selected devices.

Abstract: A pattern recognition adaptive controller configured to dynamically adjust proportional gain and integral time control parameters to minimize integrated absolute errors between a setpoint and a monitored controlled variable. The pattern recognition adaptive controller receives a sampled signal representative of the controlled variable, and determines a smoothed signal based on the sampled signal. The controller characterizes a disturbance in the smoothed signal by a damping factor and a closed loop response time. When a significant load disturbance or setpoint change occurs, the controller estimates an optimal gain based on the damping factor, and an optimal integral time based on the response time. The estimated optimal gain and estimated optimal integral time are used to determining a new gain and a new integral time values, to which the control parameters of the controller are then set.