Arm with a combined shape and force sensor

A robotic surgical system comprising:

• a surgical instrument, wherein the surgical instrument includes:
• an elongate, hollow shaft having a proximal end, a distal end, and a flexible section;
• a sensor apparatus configured to generate sensor data about the flexible section;
• and
• a force transmission mechanism coupled to the proximal end of the shaft;
• and
• a processor communicatively coupled to at least the sensor apparatus, wherein the processor is configured to receive the sensor data about the flexible section from the sensor apparatus and to use the sensor data with information regarding mechanical and material property data for the surgical instrument, including dimensional information of the surgical instrument, to determine at least one of an internal actuation force applied by the force transmission mechanism or external force information for the surgical instrument, wherein the dimensional information comprises spacing between joints of the surgical instrument.