{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,26]],"date-time":"2026-03-26T15:56:13Z","timestamp":1774540573908,"version":"3.50.1"},"reference-count":14,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2016,1,20]],"date-time":"2016-01-20T00:00:00Z","timestamp":1453248000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>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\u2013output 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.<\/jats:p>","DOI":"10.3390\/s16010127","type":"journal-article","created":{"date-parts":[[2016,1,20]],"date-time":"2016-01-20T11:19:41Z","timestamp":1453288781000},"page":"127","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Closed-Loop Control of Chemical Injection Rate for a Direct Nozzle Injection System"],"prefix":"10.3390","volume":"16","author":[{"given":"Xiang","family":"Cai","sequence":"first","affiliation":[{"name":"School of Information Science and Technology, Beijing Forestry University, Beijing 100083, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Martin","family":"Walgenbach","sequence":"additional","affiliation":[{"name":"Department of Agricultural Engineering, University of Bonn, 53115 Bonn, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Malte","family":"Doerpmond","sequence":"additional","affiliation":[{"name":"Department of Agricultural Engineering, University of Bonn, 53115 Bonn, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Peter","family":"Schulze Lammers","sequence":"additional","affiliation":[{"name":"Department of Agricultural Engineering, University of Bonn, 53115 Bonn, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yurui","family":"Sun","sequence":"additional","affiliation":[{"name":"College of Information &amp; Electrical Engineering, China Agricultural University, Beijing 100083, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2016,1,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"185","DOI":"10.1111\/j.1365-3180.2006.00504.x","article-title":"Practical experiences with a system for site-specific weed control in arable crops using real-time image analysis and GPS-controlled patch spraying","volume":"46","author":"Gerhards","year":"2006","journal-title":"Weed Res."},{"key":"ref_2","unstructured":"Lutman, P.J.W., and Miller, P.C.H. (2007). Spatially Variable Herbicide Application Technology; Opportunities for Herbicide Minimisation and Protection of Beneficial Weeds, Home-Grown Cereals Authority."},{"key":"ref_3","first-page":"101","article-title":"Generating a Digital Management Map for Variable Rate Herbicide Application Usingthe Global Positioning System","volume":"3","author":"Mohammadzamani","year":"2009","journal-title":"Am.-Eurasian J. Sustain. Agric."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"609","DOI":"10.1016\/S0261-2194(00)00080-6","article-title":"Effects of formulation on spray nozzle performance for applications from ground-based boom sprayers","volume":"19","author":"Miller","year":"2000","journal-title":"Crop Protect."},{"key":"ref_5","first-page":"8","article-title":"Droplet size and spray pattern characteristics of PWM-based continuously variable spray","volume":"2","author":"Deng","year":"2009","journal-title":"Int. J. Agric. Biol. 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Res."},{"key":"ref_10","unstructured":"Lammers, P.S., and Vondricka, J. (2010). Precision Crop Protection\u2014The Challenge and Use of Heterogeneity, Springer."},{"key":"ref_11","unstructured":"Vondricka, J. (2008). Study on the Process of Direct Nozzle Injection for Real-Time Site-Specific Pesticide Application. [Ph.D. Thesis, University of Bonn]."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"61","DOI":"10.13031\/2013.25941","article-title":"Measurement of mixture homogeneity in direct injection systems","volume":"52","author":"Vondricka","year":"2009","journal-title":"Trans. ASABE"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"49","DOI":"10.1016\/j.biosystemseng.2011.06.006","article-title":"Assessing the cleanability of a direct nozzle injection system","volume":"110","author":"Doerpmund","year":"2011","journal-title":"Biosyst. Eng."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1643","DOI":"10.13031\/2013.42347","article-title":"The challenge of cleaning direct-injection systems for pesticide application","volume":"55","author":"Doerpmund","year":"2012","journal-title":"Trans. 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