Closed-Loop Control of Chemical Injection Rate for a Direct Nozzle Injection System.
Sensors (Basel)
; 16(1)2016 Jan 20.
Article
in En
| MEDLINE
| ID: mdl-26805833
ABSTRACT
To realize site-specific and variable-rate application of agricultural pesticides, accurately metering and controlling the chemical injection rate is necessary. This study presents a prototype of a direct nozzle injection system (DNIS) by which chemical concentration transport lag was greatly reduced. In this system, a rapid-reacting solenoid valve (RRV) was utilized for injecting chemicals, driven by a pulse-width modulation (PWM) signal at 100 Hz, so with varying pulse width the chemical injection rate could be adjusted. Meanwhile, a closed-loop control strategy, proportional-integral-derivative (PID) method, was applied for metering and stabilizing the chemical injection rate. In order to measure chemical flow rates and input them into the controller as a feedback in real-time, a thermodynamic flowmeter that was independent of chemical viscosity was used. Laboratory tests were conducted to assess the performance of DNIS and PID control strategy. Due to the nonlinear input-output characteristics of the RRV, a two-phase PID control process obtained better effects as compared with single PID control strategy. Test results also indicated that the set-point chemical flow rate could be achieved within less than 4 s, and the output stability was improved compared to the case without control strategy.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Pesticides
/
Agrochemicals
/
Agriculture
/
Engineering
Language:
En
Journal:
Sensors (Basel)
Year:
2016
Document type:
Article
Affiliation country:
China