*Article* **Experimental Research for Digging and Inverting of Upright Peanuts by Digger-Inverter**

**Haiyang Shen 1,2, Hongguang Yang 1, Qimin Gao 1,2, Fengwei Gu 1, Zhichao Hu 1,2,\*, Feng Wu 1, Youqing Chen <sup>1</sup> and Mingzhu Cao <sup>1</sup>**

> <sup>1</sup> Nanjing Institute of Agricultural Mechanization, Ministry of Agriculture and Rural Affairs, Nanjing 210014, China; 82101221060@caas.cn (H.S.); yanghongguang@caas.cn (H.Y.); qmgao93@163.com (Q.G.); wufeng@caas.cn (F.W.); chenyouqing@caas.cn (Y.C.); caomingzhu@caas.cn (M.C.)

<sup>2</sup> Graduate School of Chinese Academy of Agricultural Sciences, Beijing 100081, China

**\*** Correspondence: huzhichao@caas.cn

**Abstract:** In order to quickly dry the peanut pods and effectively reduce the mildew on peanut pods in rainy weather, this paper analyzed the research status of peanut digging and inverting technology in China and abroad, combined with the peanut two-stage harvesting mode. The orthogonal experiment was carried out by using the peanut digger-inverter to study the different forms of upright type, taking the rate of vines inverting, the rate of buried pods, and the rate of fallen pods as the evaluation indexes, and taking the traveling speed of the tractor A, the line speed of the conveyor chain B, and the line speed of the inverting roller C as the experimental factors. The results showed that, in the states of unpressed vines and pressed vines, the order of influence of the peanut digger-inverter on the evaluation indices was A > C > B. The optimal horizontal combination of unpressed vines was A2C3B2, when the traveling speed of the tractor is 1.06 m/s, the line speed of the inverting roller is 2.12 m/s, and the line speed of the conveyor chain is 1.02 m/s; the rate of vines inverting was 71.07%, the rate of buried pods was 0.2%, and the rate of fallen pods was 0.22%. Under the condition of vines pressing, the best horizontal combination is A2C2B2, when the travelling speed of the tractor is 1.01 m/s, the line speed of the inverting roller is 1.88 m/s, and the line speed of the conveyor chain is 1.02 m/s; the rate of vines inverting was 74.29%, the rate of buried pods was 0.14%, and the rate of fallen pods was 0.33%. The paired *t*-test was carried out by the peanut digger-inverter under the state of pressed and unpressed vines. There was little difference in the influence of each factor on the rate of fallen pods and the rate of buried pods, but there was a significant difference in the influence on the rate of vines inverting. The rate of inversion of vines under the state of pressed vines was higher than that under the state of unpressed vines. The research results will provide certain technical support for the late optimization of the peanut digger-inverter and create a hardware foundation for the intelligence and information harvesting of peanuts.

**Keywords:** agricultural machinery; peanuts; digger-inverter; orthogonal experiment; paired *t*-test; unpressed vines; pressed vines
