Methods and systems for planning a body position of a robotic device

A non-transitory computer readable medium having stored thereon instructions that, upon execution by a computing device, cause the computing device to perform functions comprising:

• receiving a reference step path that comprises a plurality of spatial points that each define a predetermined step location for an end component of a robotic device, wherein the robotic device has a plurality of appendages and the plurality of appendages are connected to a body of the robotic device, wherein the end component is connected to a distal end of a given appendage of the plurality of appendages;
• receiving a set of constraints comprising a length of the given appendage and a gravitational force experienced by the body of the robotic device;
• receiving a predetermined height and a predetermined pitch of the body for the robotic device to maintain a balance;
• assigning a cost to each of a height of the body, a height acceleration of the body, and a pitch acceleration of the body;
• determining a new height and a new pitch of the body that reduces the height acceleration and the pitch acceleration of the body when the end component moves along the reference step path, based on i) the reference step path, ii) the set of constraints, iii) the predetermined height and the predetermined pitch of the body and iv) the cost to each of the height of the body, the height acceleration of the body, and the pitch acceleration of the body;
• and
• instructing the robotic device to actuate the plurality of appendages to achieve the new height and the new pitch of the body when the end component moves along the reference step path.

A robotic device comprising:

• a body;
• a plurality of appendages that are connected to the body of the robotic device;
• a plurality of end components, and each respective end component is connected to a respective distal end of a respective appendage of the plurality of appendages;
• a processor;
• and
• a non-transitory computer readable medium having stored thereon instructions that, when executed by the processor, cause the robotic device to perform functions comprising:
• receiving a reference step path that comprises a plurality of spatial points that define a predetermined location for the given end component of the robotic device;
• receiving a set of constraints comprising a length of the given appendage and a gravitational force experienced by the body of the robotic device;
• receiving a predetermined height and a predetermined pitch of the body for the robotic device to maintain a balance;
• assigning a cost to each of a height of the body, a height acceleration of the body, and a pitch acceleration of the body;
• determining a new height trajectory and a new pitch trajectory of the body that reduces the height acceleration and the pitch acceleration of the body when the end component moves along the reference step path, based on i) the reference step path, ii) the set of constraints, iii) the predetermined height and the predetermined pitch of the body and iv) the cost to each of the height of the body, the height acceleration of the body, and the pitch acceleration of the body;
• and
• instructing the robotic device to actuate the plurality of appendages to achieve the new height and the new pitch of the body when the end component moves along the reference step path.