## 1 _Article_  
Design and Experimental Evaluation of a Form Trimming Machine for Horticultural Plants  
**[PERSON] 1,2,** [PERSON] 1,2, [PERSON] 1,2, [PERSON] 1,2,*(r), [PERSON] 1 and [PERSON] 1  
1 College of Engineering, Huazhong Agricultural University, Wuhan 430070, China; [EMAIL_ADDRESS] (M.L. ); [EMAIL_ADDRESS] (L.M. ); [EMAIL_ADDRESS] (W.Z. ); [EMAIL_ADDRESS] (M.H. ); [EMAIL_ADDRESS] (YS.) 2 Key Laboratory of Agricultural Equipment in Mid-Lower Yangtze River, Ministry of Agriculture and Rural Affairs, Wuhan 430070, China
* Correspondence: [EMAIL_ADDRESS]; Tel. : +86-27-8728-2120  
**Citation:** [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON] [PERSON] Design and Experimental Evaluation of a Form Trimming Machine for Horticultural Plants. is relatively low, especially in China [6]. Currently, form trimming of shrubs is mainly performed by human operators using handheld shears and trimmers. Obvious disadvantages include high human labor input, low productivity and inconsistent performance. Therefore, to provide a time-and-energy efficient solution for shrub trimming is of great value in promoting horticultural mechanization. Through a comprehensive literature survey, there exists a significant body of work on trimming machines for various plants, such as grass [7, 8], coconut [9], spinach [10, 11], and hedge [12]. However, there are very few studies on form trimming of shrubs or bushes. Since each plant has its particular physical and mechanical properties, and the trimming requirements for different plants vary, the structural designs of those trimming machines cannot be directly applied in form trimming for shrubs. The most recent work on shrub trimming is reported in [13], in which a robotic arm with a vision system and a motion planning algorithm was developed. A circular double-blade cutter was mounted onto the robotic arm as the end-effector and was guided by the motion planning algorithm to cut a shrub plant into a designed shape. The accuracy of the system was tested to be lower than required, and further improvement on the vision system was suggested. Some machinery companies in Europe, such as Orlandi Group of Italy and Lanz Technik of Germany, have produced ground support trimming machines for form trimming of plants to reduce human labor demand. However, the design principles of those machines were not clear and no performance evaluation were performed. Cutters and blades are important working parts in trimming machines for agriculture and horticulture. A series of work were conducted on designing suitable cutting elements and determining their optimal working parameters for trimming crops [14, 15, 16], fruit trees [17, 18, 19] and landscaping plants [20] etc. Such as in [21], the optimal combination of cutting speed, cutting gap and blade level angle were experimentally determined for the moving blade of a trimming tool for longan branches, and in [22], the optimal fruit feeding rate, rotating speed of the trimmed fruit and the knife height were experimentally determined for an automatic trimming machine for young coconut fruit. Overall, there are two main types of cutters used for plant cutting and trimming: disc type and blade type. Disc cutters are commonly used in cutting crops, vegetables, grasses and tree twigs through continuous rotations. The blade type can have various mechanical configurations, such as single moving blade, double moving blades, double blades with one blade moving and one fixed, multiple blades, and various motion types: circular, angular, and linear. Currently, the blade type cutters with linear reciprocating motion are mainly used in agricultural harvesters for grain crops. Double blade cutters, with one set of linearly moving blades or two sets of oppositely moving blades, are commonly seen on trimmers of tree branches and hedges. These machines are usually handheld, and form trimming cannot be realized without human operators' maneuvers.