  Increasingly complex and autonomous systems require machine ethics to
maximize the benefits and minimize the risks to society arising from the new
technology. It is challenging to decide which type of ethical theory to employ
and how to implement it effectively. This survey provides a threefold
contribution. First, it introduces a trimorphic taxonomy to analyze machine
ethics implementations with respect to their object (ethical theories), as well
as their nontechnical and technical aspects. Second, an exhaustive selection
and description of relevant works is presented. Third, applying the new
taxonomy to the selected works, dominant research patterns, and lessons for the
field are identified, and future directions for research are suggested.
