K. C. Ting

Visual feedback guided robotic cherry tomato harvesting

Harvesting cherry tomatoes is more laborious than harvesting larger size tomatoes because of the high fruit density in every cluster. To save labor costs, robotic harvesting of cherry tomatoes has been studied in Japan. An effective vision algorithm, to detect positions of many small fruits, was developed for guidance of robotically harvested cherry tomatoes. A spectral reflectance in the visible region was identified and extracted to provide high contrast images for the fruit cluster identification. The 3-D position of each fruit cluster was determined using a binocular stereo vision technique. The robot harvested one fruit at a time and the position of the next target fruit was updated based on a newly acquired image and the latest manipulator position. The experimental results showed that this visual feedback control based harvesting method was effective, with a success rate of 70%.

End-Effectors for Tomato Harvesting Robot

Two types of robotic end-effectors capable of harvesting tomato fruits were manufactured based on the physical properties of tomato plant and tested. The first prototype end-effector consisted of two parallel plate fingers and a suction pad. The fingers pick a fruit off at the joint of its peduncle after the suction cup singulates it by vacuum from other fruits in the same cluster. From the results of harvesting experiment, the end-effector could not harvest fruits with a short peduncle because the fruits were detached from the suction pad before they were gripped by the fingers. Therefore, the second prototype in which the functions to detect the fruit position and the air pressure in the pad were installed, was made, so that the fruits were harvested regardless of the length of their peduncle. Experimental results using the improved end-effector showed that the fruits were harvested successfully with no damage.

Robotics for Plant Production

Applying robotics in plant production requires the integration of robot capabilities, plant culture, and the work environment. Commercial plant production requires certain cultural practices to be performed on the plants under certain environmental conditions. Some of the environmental conditions are mostly natural and some are modified or controlled. In many cases, the required cultural practices dictate the layout and materials flow of the production system. Both the cultural and environmental factors significantly affect when, where and how the plants are manipulated. Several cultural practices are commonly known in the plant production industry. The ones which have been the subject of robotics research include division and transfer of plant materials in micropropagation, transplanting of seedlings, sticking of cuttings, grafting, pruning, and harvesting of fruit and vegetables. The plants are expected to change their shape and size during growth and development. Robotics technology includes many sub-topics including the manipulator mechanism and its control, end-effector design, sensing techniques, mobility, and workcell development. The robots which are to be used for performing plant cultural tasks must recognize and understand the physical properties of each unique object and must be able to work under various environmental conditions in fields or controlled environments. This article will present some considerations and examples of robotics development for plant production followed by a description of the key components of plant production robots. A case study on developing a harvesting robot for an up-side-down single truss tomato production system will also be described.

Robot workcell for transplanting of seedlings. Part II. End-effector development

ABSTRACT The successful integration of a robot with seedling transplanting requires an operational end-effector. Two types of grippers were designed in this study for seedling picking, holding, and planting during robotic transplanting. They were called Swinging Needles and Sliding Needles, respectively. The Sliding Needles gripper was found to be functionally superior to the Swinging Needles for seedling transplanting. Further study was done to incorporate a seedling sensing capability to the Sliding Needles gripper. A capacitive proximity sensor was selected and its sensing capability tested on plant materials. The sensor was found to have satisfactory performance in terms of detecting seedlings held by the gripper. The sensor and the gripper were then integrated to become a final end-effector design called Sliding Needles with Sensor. A prototype of the final design version was tested. The gripper was adaptable to a wide range of seedling sizes and shapes. The sensor on the gripper assured that the growing flats were transplanted with seedlings of satisfactory quality.

Machine Vision Assisted Robotic Seedling Transplanting

A machine vision assisted robotic transplanter was developed to improve the quality of the grow-out trays that contain transplanted plugs. The machine vision system was designed to identify and locate empty positions in the transplanted seedling trays. The detection algorithm was able to inspect uneven height growth medium blocks in randomly oriented seedling trays. Fifteen species of seedlings were used in evaluating the integrated machine vision assisted robotic system. The overall vision system success rate in identifying mistransplanted empty growth medium blocks in the transplanted seedling trays is 95%.

Availability of Solar Photosynthetically Active Radiation

ABSTRACT THE ability to predict the amount of photosyntheti-cally active radiation (PAR) from the sun for field crops or within a particular greenhouse design is useful. PAR is a portion (0.4-0.7 micrometer wavelength) of the total radiation spectrum directly related to plant photosynthetic productivity. While total solar radiation data are readily available for many locations around the world, the published information on PAR is lacking. Experiments have been conducted to determine the correlations between the available hourly and daily PAR and total solar radiation. PAR was measured in the photon flux density unit of mol s^ m^ and total radiation was in the radiant flux density of W m^. Regression equations are presented in this paper for two purposes: (a) to show the predictability of PAR using available total solar radiation data, and (b) to provide empirical equations for estimating direct and diffuse PAR based on total radiation values.

ROBOT WORKCELL FOR TRANSPLANTING OF SEEDLINGS PART I - LAYOUT AND MATERIALS FLOW

ABSTRACT The transplanting of seedlings from high density plug trays into low density growing flats, as currently practiced in the bedding plant production systems, was the operation studied within a prototype workcell utilizing a Selective Compliance Assembly Robot Arm (SCARA) type robot. The concept of a multi-stop local work trajectory surrounding each seedling was incorporated into the workcell design consideration. The trays and flats were envisioned to flow across each others path at different heights within the workcell. A straight-line robot wrist motion was used between the locations on a tray and a flat. A computer program for checking the interactions of the workcell layout, the robot motions and the flows of materials was developed. The average robot wrist horizontal travel distance per transplanting (AHT) for a given workcell could be readily calculated using this computer program. The AHT was evaluated for its use as an indication of the performance of any given workcell design. For the 12 cases studied, the AHT ranged from 0.381 m to 0.993 m which was found to correlate well with the average cycle time per transplanting.

Solar photosynthetically active radiation transmission through greenhouse glazings

Abstract One critical factor for crop energy conversion for plant growth is photosynthetically active radiation (PAR) received by the plant. While it is important to know their total solar radiation transmission characteristics in the design of greenhouse for thermal environment management, it is also essential to understand their PAR transmission capability, especially over the winter period for high-latitude regions. This paper presents the results of PAR transmission of four different greenhouse glazings, measured at both the glazing and crop canopy levels. The glazings studied were single glass, double glass, twin-walled acrylic and air-inflated double polyethylene. The first three materials were tested at a commercial rose greenhouse range (gable type) in Connecticut and the double polyethylene greenhouse (bow type) was located at Cook College, Rutgers University. Also reported is the comparison between total solar radiation transmission and PAR transmission in the double polyethylene greenhouse. The glazing level PAR transmission showed mainly the effects of glazing materials, sky clearness and solar angle of incidence, whereas PAR received at the canopy level was strongly influenced by the greenhouse geometric configuration and internal structures. It was found that air-inflated double polyethylene transmitted a higher percentage when measured in the total solar radiation range than in the PAR range.

Factors affecting performance of sliding-needles gripper during robotics transplanting of seedlings

Transplanting tests with commercially grown seedling plugs were conducted using a Sliding-Needles with Sensor (SNS) gripper operated by a SCARA type robot. A total of 11 plug trays, with 600 cells each, were tested. Many mechanical and horticultural factors were found to affect the percentage of successful transplanting, which were analyzed to understand their influence on the effectiveness of the gripper. The mechanical factors were 1) the angles of gripper needles; 2) plug extraction acceleration; and 3) the sensor sensitivity. The horticultural factors included 1) empty cells on the plug trays; 2) plant species; 3) root connections; 4) adhesion between roots and cell walls; 5) root zone moisture; and 6) the number of seedlings in one cell.

Animated simulation of greenhouse internal transport using Siman/Cinema

ABSTRACT An animated computer model has been developed using a simulation language SIMAN/CINEMA to simulate greenhouse internal transport systems. The model can be used as a tool to study the performance of materials handling operations within a greenhouse. The potential bottleneck of a transport system can be visually detected on the computer monitor. Statistical analyses on the system parameters, such as the status and utilization of machines, workers and waiting lines, and throughput time of an operation, are performed during the simulation. From these data, the interaction between machines and workers within a greenhouse system can be studied.