updates

src/pid/index.js

@@ -1,11 +1,14 @@
-const PIDController = require('./PIDController');
+const { PIDController, CascadePIDController } = require('./PIDController');
 
 /**
- * Convenience factory for one-line instantiation.
+ * Convenience factories.
  */
 const createPidController = (options) => new PIDController(options);
+const createCascadePidController = (options) => new CascadePIDController(options);
 
 module.exports = {
   PIDController,
-  createPidController
+  CascadePIDController,
+  createPidController,
+  createCascadePidController,
 };