"原型机研制" can be translated into English as "development of the prototype machine" or "prototyping (of a machine)".
"Development of the prototype machine" emphasizes the process of creating and refining the initial version of a machine for testing and validation.
"Prototyping (of a machine)" is a more concise term that specifically refers to the act of building a prototype, which is an early sample, model, or release of a product built to test a concept or process.
Both translations are accurate and can be used depending on the context and the level of detail required.